Bicycle sprocket

ABSTRACT

A bicycle sprocket includes a sprocket body, and a plurality of sprocket teeth. At least one of the sprocket teeth includes a first layered member, a second layered member and a third layered member. The first layered member has a first axial surface and a second axial surface. The second layered member is attached to the first axial surface such that the first and second layered members overlap each other in an axial direction as viewed parallel to a rotational axis of the sprocket body. The third layered member is attached to the second axial surface such that the first and third layered members overlap each other in the axial direction as viewed parallel to the rotational axis of the sprocket body. The first layered member has a specific gravity that is less than those of the second layered member and the third layered member.

BACKGROUND

1. Field of the Invention

This invention generally relates to a bicycle sprocket. Morespecifically, the present invention relates to a bicycle sprocket with amulti-layered structure.

2. Background Information

In recent years, bicycle component manufacturers have been manufacturingbicycle transmissions that have more available speeds to the rider. Asthe available speeds in the bicycle transmission increases, the numberof sprockets installed on the rear wheel also usually increases. Whilesprockets can be made thinner, a minimum spacing between adjacentsprockets is required to accommodate the chain. Moreover, a rear end ofa conventional bicycle frame only has a limited amount of space formounting the wheel and a rear sprocket assembly. Thus, there is a desireto increase the number gears without changing the dimensions of theconventional bicycle frame. Accordingly, various attempts have been madein order to increase the maximum number of sprocket that can beinstalled on a rear hub assembly. For example, some multiple sprocketassemblies use a spider (sprocket support), which supports a pluralityof ring-shaped sprocket wheels. By using a spider, a light metal such asaluminum, etc., is generally used for the spider, while various types ofsteel materials are used for the sprockets to provide adequate strength.

SUMMARY

Generally, the present disclosure is directed to various features of abicycle sprocket with a multi-layered structure. Thus, one object of thepresent disclosure is to provide a bicycle sprocket with a multi-layeredstructure.

In accordance with a first aspect of the present invention, a bicyclesprocket is provided that basically includes a sprocket body, and aplurality of sprocket teeth. The sprocket body has a rotational axis.The sprocket teeth extend radially outwardly from an outer periphery ofthe sprocket body. At least one of the sprocket teeth includes a firstlayered member, a second layered member and a third layered member. Thefirst layered member has a first axial surface and a second axialsurface opposite to the first axial surface. The second layered memberis attached to the first axial surface of the first layered member suchthat the first and second layered members overlap each other in an axialdirection as viewed parallel to the rotational axis. The third layeredmember is attached to the second axial surface of the first layeredmember such that the first and third layered members overlap each otherin the axial direction as viewed parallel to the rotational axis. Thefirst layered member has a specific gravity that is less than those ofthe second layered member and the third layered member. According to thefirst aspect of the present invention, it is possible to effectivelysave weight of the bicycle sprocket while maintaining necessaryrigidity.

In accordance with a second aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that each of thefirst, second and third layered members has an axial thickness more thanor equal to 0.1 mm. According to the second aspect of the presentinvention, it is possible to effectively obtain necessary rigidity ofeach of the first, second and the third layered members.

In accordance with a third aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that the firstand second layered members do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis, and thefirst and third layered members do not overlap each other in the radialdirection as viewed perpendicularly to the rotational axis. According tothe third aspect of the present invention, it is possible to effectivelymanufacture the bicycle sprocket by simply attach each of the second andthird layered members to the first layered members in the axialdirection.

In accordance with a fourth aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that thesprocket body includes the first layered member, the second layeredmember and the third layered member. According to the fourth aspect ofthe present invention, it is possible to further effectively save weightof the bicycle sprocket because the layered structure extends from thesprocket teeth to the sprocket body.

In accordance with a fifth aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that the firstlayered member is made of a material selected from the group consistingof aluminum, titanium, magnesium and beryllium. According to the fifthaspect of the present invention, it is possible to effectively saveweight of the bicycle sprocket because of such light weight metallicmaterials.

In accordance with a sixth aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that the firstlayered member is made of non-metallic material. According to the sixthaspect of the present invention, it is possible to select lightweightmaterials to realize further save weight of the bicycle sprocket.

In accordance with a seventh aspect of the present invention, thebicycle sprocket according to the sixth aspect is configured so that thenon-metallic material of the first layered member includes resin.According to the seventh aspect of the present invention, it is possibleto select lightweight materials to realize further save weight of thebicycle sprocket because of resin.

In accordance with an eighth aspect of the present invention, thebicycle sprocket according to the seventh aspect is configured so thatthe non-metallic material of the first layered member isfiber-reinforced material. According to the eighth aspect of the presentinvention, because of the fiber-reinforced material, it is possible toselect lightweight materials to realize further save weight of thebicycle sprocket while maintaining necessary rigidity.

In accordance with a ninth aspect of the present invention, the bicyclesprocket according to the first aspect is configured so that the secondand third layered members are made of iron. According to the ninthaspect of the present invention, it is possible to effectively obtainnecessary rigidity of the bicycle sprocket because of high rigidity ofiron.

In accordance with a tenth aspect of the present invention, the bicyclesprocket according to the ninth aspect is configured so that the secondand third layered members are made of stainless steel. According to thetenth aspect of the present invention, it is possible to effectivelyprevent rust of the bicycle sprocket because of characteristic ofstainless steel while obtaining necessary rigidity of the bicyclesprocket because of high rigidity of steel.

In accordance with an eleventh aspect of the present invention, thebicycle sprocket according to the fifth aspect is configured so that thesecond and third layered members are made of iron. According to theeleventh aspect of the present invention, it is possible to effectivelysave weight of the bicycle sprocket because of such light weightmetallic materials of the fifth aspect while maintaining necessaryrigidity because of high rigidity of iron.

In accordance with a twelfth aspect of the present invention, thebicycle sprocket according to the eleventh aspect is configured so thatthe second and third layered members are made of stainless steel.According to the twelfth aspect of the present invention, it is possibleto effectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel while obtaining necessary rigidity ofthe bicycle sprocket because of high rigidity of iron besideseffectively saving weight of the bicycle sprocket because of such lightweight metallic materials of the fifth aspect.

In accordance with a thirteenth aspect of the present invention, thebicycle sprocket according to the sixth aspect is configured so that thesecond and third layered members are made of iron. According to thethirteenth aspect of the present invention, it is possible toeffectively obtain necessary rigidity of the bicycle sprocket because ofhigh rigidity of iron besides the advantage of the sixth aspect of thepresent invention.

In accordance with a fourteenth aspect of the present invention, thebicycle sprocket according to the thirteenth aspect is configured sothat the second and third layered members are made of stainless steel.According to the fourteenth aspect of the present invention, it ispossible to effectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel besides of the advantage of thethirteenth aspect of the present invention.

In accordance with a fifteenth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that thefirst layered member and the second layered member are attached to eachother by diffusion bonding, and the first layered member and the thirdlayered member are attached to each other by diffusion bonding.According to the fifteenth aspect of the present invention, it ispossible to firmly attach each of the second and third layered membersto the first layered member.

In accordance with a sixteenth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that thefirst layered member and the second layered member are attached to eachother with an adhesive, and the first layered member and the thirdlayered member are attached to each other with an adhesive. According tothe sixteenth aspect of the present invention, it is possible toinexpensively attach each of the second and third layered members to thefirst layered member.

In accordance with a seventeenth aspect of the present invention, thebicycle sprocket according to the seventh aspect is configured so thatthe first layered member and the second layered member are attached toeach other by an integral molding process, and the first layered memberand the third layered member are attached to each other by an integralmolding process. According to the seventeenth aspect of the presentinvention, it is possible to effectively and quickly manufacture thebicycle sprockets.

In accordance with an eighteenth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that theplurality of sprocket teeth includes the first layered member, thesecond layered member and the third layered member. According to theeighteenth aspect of the present invention, it is possible to furthersave weight of the bicycle sprocket while maintaining necessaryrigidity.

In accordance with a nineteenth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that thesecond layered member has a specific gravity that is equal to that ofthe third layered member. According to the nineteenth aspect of thepresent invention, it is possible to effectively improve weightdistribution of the bicycle sprocket.

In accordance with a twentieth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that theat least one of the sprocket teeth further includes a coating layerformed on a radially end surface of the first layered member. Accordingto the twentieth aspect of the present invention, it is possible toimprove wear resistance of the first layered member.

In accordance with a twenty-first aspect of the present invention, thebicycle sprocket according to the twentieth aspect is configured so thatthe coating layer is an intermetallic compound layer. According to thetwenty-first aspect of the present invention, it is possible toeffectively improve wear resistance of the first layered member.

In accordance with a twenty-second aspect of the present invention, thebicycle sprocket according to the twenty-first aspect is configured sothat the intermetallic compound layer is made of aluminum, and one ofnickel and iron. According to the twenty-second aspect of the presentinvention, it is possible to effectively improve wear resistance of thefirst layered member.

In accordance with a twenty-third aspect of the present invention, thebicycle sprocket according to the twentieth aspect is configured so thatthe coating layer is a plated layer. According to the twenty-thirdaspect of the present invention, it is possible to effectively improvewear resistance of the first layered member.

In accordance with a twenty-fourth aspect of the present invention, thebicycle sprocket according to the twenty-third aspect is configured sothat the coating layer is a nickel-plated layer. According to thetwenty-fourth aspect of the present invention, it is possible toeffectively improve wear resistance of the first layered member.

In accordance with a twenty-fifth aspect of the present invention, thebicycle sprocket according to the tenth aspect is configured so that thesecond and third layered members have Vickers hardness larger than orequal to 400 (HV), respectively. According to the twenty-fifth aspect ofthe present invention, it is possible to effectively obtain necessaryrigidity of the second and third layered members.

In accordance with a twenty-sixth aspect of the present invention, thebicycle sprocket according to the fifth aspect is configured so that thefirst layered member is made of quenched aluminum. According to thetwenty-sixth aspect of the present invention, it is possible toeffectively improve rigidity of the first layered member.

In accordance with a twenty-seventh aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that thefirst layered member extends radially inwardly from an inner peripheryof the sprocket body, and the first layered member has an axiallyprojecting portion and an axially recessed portion. The axiallyprojecting portion and the axially recessed portion are positionedradially inwardly from the inner periphery of the sprocket body.According to the twenty-seventh aspect of the present invention, it ispossible to provide bicycle sprockets which are easily attached to eachother to form a multiple bicycle sprocket assembly.

In accordance with a twenty-eighth aspect of the present invention, thebicycle sprocket according to the twenty-seventh aspect is configured sothat the first layered member has a bicycle hub engaging profile at alocation of a radially inner end of the first layered member. Accordingto the twenty-eighth aspect of the present invention, it is possible toprovide a multiple rear sprocket assembly which is lightweight and hassufficient rigidity.

In accordance with a twenty-ninth aspect of the present invention, thebicycle sprocket according to the first aspect is configured so that thesprocket body has an axially projecting portion and an axially recessedportion. The axially projecting portion and the axially recessed portionare positioned at the sprocket body. According to the twenty-ninthaspect of the present invention, it is possible to provide bicyclesprockets which are easily attached to each other to form a multiplebicycle sprocket assembly.

In accordance with a thirtieth aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the twenty-seventhaspect. The axially projecting portion of one of the bicycle sprocketsmates with the axially recessed portion of an adjacent one of thebicycle sprockets adjacent to the one of the bicycle sprockets while thebicycle sprockets are attached to each other. According to the thirtiethaspect of the present invention, it is possible to provide a multiplebicycle sprocket assembly which is lightweight and has sufficientrigidity.

In accordance with a thirty-first aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the first aspect, and asprocket support member to which the bicycle sprockets are mounted.According to the thirty-first aspect of the present invention, it ispossible to provide a multiple bicycle sprocket assembly which islightweight and has sufficient rigidity.

In accordance with a thirty-second aspect of the present invention, themultiple sprocket assembly according to the thirty-first aspect isconfigured so that the sprocket support member has a unitary one-piecestructure. According to the thirty-second aspect of the presentinvention, it is possible to provide a multiple bicycle sprocketassembly which is lightweight and has sufficient rigidity.

In accordance with a thirty-third aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the twenty-ninth aspect.The axially projecting portion of one of the bicycle sprockets mateswith the axially recessed portion of an adjacent one of the bicyclesprockets adjacent to the one of the bicycle sprockets while the bicyclesprockets are attached to each other. According to the thirty-thirdaspect of the present invention, it is possible to provide a multiplebicycle sprocket assembly which is lightweight and has sufficientrigidity.

In accordance with a thirty-fourth aspect of the present invention, abicycle sprocket is provided that basically includes a sprocket body,and a plurality of sprocket teeth. The sprocket body has a rotationalaxis. The sprocket teeth extend radially outwardly from an outerperiphery of the sprocket body. At least one of the sprocket teethincluding a first layered member, a second layered member and a coatinglayer formed on a radially end surface of the first layered member. Thefirst and second layered members are attached to each other such thatthe first and second layered members overlap each other in an axialdirection as viewed parallel to the rotational axis and such that thefirst and second layered members do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis. The firstlayered member has a specific gravity that is less than that of thesecond layered member. According to the thirty-fourth aspect of thepresent invention, it is possible to effectively save weight of thebicycle sprocket while maintaining necessary rigidity, and further toimprove wear resistance of the first layered member.

In accordance with a thirty-fifth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat each of the first and second layered members has an axial thicknessmore than or equal to 0.1 mm. According to the thirty-fifth aspect ofthe present invention, it is possible to effectively obtain necessaryrigidity of each of the first and second layered members.

In accordance with a thirty-sixth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the sprocket body includes the first layered member and the secondlayered member. According to the thirty-sixth aspect of the presentinvention, it is possible to further effectively save weight of thebicycle sprocket because the layered structure extends from the sprocketteeth to the sprocket body.

In accordance with a thirty-seventh aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the coating layer is an intermetallic compound layer. According tothe thirty-seventh aspect of the present invention, it is possible toeffectively improve wear resistance of the first layered member.

In accordance with a thirty-eighth aspect of the present invention, thebicycle sprocket according to the thirty-seventh aspect is configured sothat the intermetallic compound layer is made of aluminum, and one ofnickel and iron. According to the thirty-eighth aspect of the presentinvention, it is possible to effectively improve wear resistance of thefirst layered member.

In accordance with a thirty-ninth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the coating layer is a plated layer. According to the thirty-ninthaspect of the present invention, it is possible to effectively improvewear resistance of the first layered member.

In accordance with a fortieth aspect of the present invention, thebicycle sprocket according to the thirty-ninth aspect is configured sothat the coating layer is a nickel-plated layer. According to thefortieth aspect of the present invention, it is possible to effectivelyimprove wear resistance of the first layered member.

In accordance with a forty-first aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.According to the forty-first aspect of the present invention, it ispossible to effectively save weight of the bicycle sprocket because ofsuch light weight metallic materials.

In accordance with a forty-second aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the second layered member is made of iron. According to theforty-second aspect of the present invention, it is possible toeffectively obtain necessary rigidity of the bicycle sprocket because ofhigh rigidity of iron.

In accordance with a forty-third aspect of the present invention, thebicycle sprocket according to the forty-second aspect is configured sothat the second layered member is made of stainless steel. According tothe forty-third aspect of the present invention, it is possible toeffectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel while obtaining necessary rigidity ofthe bicycle sprocket because of high rigidity of steel.

In accordance with a forty-fourth aspect of the present invention, thebicycle sprocket according to the forty-third aspect is configured sothat the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.According to the forty-fourth aspect of the present invention, it ispossible to effectively save weight of the bicycle sprocket because ofsuch light weight metallic materials.

In accordance with a forty-fifth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member is made of non-metallic material.According to the forty-fifth aspect of the present invention, it ispossible to select lightweight materials to realize further save weightof the bicycle sprocket.

In accordance with a forty-sixth aspect of the present invention, thebicycle sprocket according to the forty-fifth aspect is configured sothat the non-metallic material of the first layered member includesresin. According to the forty-sixth aspect of the present invention, itis possible to select lightweight materials to realize further saveweight of the bicycle sprocket because of resin.

In accordance with a forty-seventh aspect of the present invention, thebicycle sprocket according to the forty-sixth aspect is configured sothat the non-metallic material of the first layered member isfiber-reinforced material. According to the forty-seventh aspect of thepresent invention, because of the fiber-reinforced material, it ispossible to select lightweight materials to realize further save weightof the bicycle sprocket while maintaining necessary rigidity.

In accordance with a forty-eighth aspect of the present invention, thebicycle sprocket according to the forty-fifth aspect is configured sothat the second layered member is made of iron. According to theforty-eighth aspect of the present invention, it is possible toeffectively obtain necessary rigidity of the bicycle sprocket because ofhigh rigidity of iron.

In accordance with a forty-ninth aspect of the present invention, thebicycle sprocket according to the forty-eighth aspect is configured sothat the second layered member is made of stainless steel. According tothe forty-ninth aspect of the present invention, it is possible toeffectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel while obtaining necessary rigidity ofthe bicycle sprocket because of high rigidity of steel.

In accordance with a fiftieth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member and the second layered member are attachedto each other by diffusion bonding. According to the fiftieth aspect ofthe present invention, it is possible to firmly attach the secondlayered member to the first layered member.

In accordance with a fifty-first aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member and the second layered member are attachedto each other with an adhesive. According to the fiftieth aspect of thepresent invention, it is possible to inexpensively attach the secondlayered member to the first layered member.

In accordance with a fifty-second aspect of the present invention, thebicycle sprocket according to the forty-sixth aspect is configured sothat the first layered member and the second layered member are attachedto each other by an integral molding process. According to thefifty-second aspect of the present invention, it is possible toeffectively and quickly manufacture the bicycle sprockets.

In accordance with a fifty-third aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member has a first axial surface and a secondaxial surface opposite to the first axial surface, the second layeredmember is attached to the first axial surface of the first layeredmember, and the at least one of the sprocket teeth further includes athird layered member. The third layered member is attached to the secondaxial surface of the first layered member such that the first and thirdlayered members overlap each other in the axial direction as viewedparallel to the rotational axis and such that the first and thirdlayered members do not overlap each other in the radial direction asviewed perpendicularly to the rotational axis. According to thefifty-third aspect of the present invention, it is possible to furtherimprove the rigidity of the bicycle sprocket of the thirty-forth aspectbecause of the additional third layered member.

In accordance with a fifty-fourth aspect of the present invention, thebicycle sprocket according to the fifty-third aspect is configured sothat the sprocket body includes the first layered member, the secondlayered member and the third layered member. According to thefifty-fourth aspect of the present invention, it is possible to furthereffectively save weight of the bicycle sprocket because the layeredstructure extends from the sprocket teeth to the sprocket body.

In accordance with a fifty-fifth aspect of the present invention, thebicycle sprocket according to the forty-third aspect is configured sothat the second layered member has Vickers hardness larger than or equalto 400 (HV). According to the fifty-fifth aspect of the presentinvention, it is possible to effectively obtain necessary rigidity ofthe second layered member.

In accordance with a fifty-sixth aspect of the present invention, thebicycle sprocket according to the forty-first aspect is configured sothat the first layered member is made of quenched aluminum. According tothe fifty-sixth aspect of the present invention, it is possible toeffectively improve rigidity of the first layered member.

In accordance with a fifty-seventh aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the plurality of sprocket teeth includes the first layered memberand the second layered member. According to the fifty-seventh aspect ofthe present invention, it is possible to further save weight of thebicycle sprocket while maintaining necessary rigidity.

In accordance with a fifty-eighth aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the first layered member extends radially inwardly from an innerperiphery of the sprocket body, and the first layered member has anaxially projecting portion and an axially recessed portion. The axiallyprojecting portion and the axially recessed portion are positionedradially inwardly from the inner periphery of the sprocket body.According to the fifty-eighth aspect of the present invention, it ispossible to provide bicycle sprockets which are easily attached to eachother to form a multiple bicycle sprocket assembly.

In accordance with a fifty-ninth aspect of the present invention, thebicycle sprocket according to the fifty-eighth aspect is configured sothat the first layered member has a bicycle hub engaging profile at alocation of a radially inner end of the first layered member. Accordingto the fifty-ninth aspect of the present invention, it is possible toprovide a multiple rear sprocket assembly which is lightweight and hassufficient rigidity.

In accordance with a sixtieth aspect of the present invention, thebicycle sprocket according to the fifty-eighth aspect is configured sothat the sprocket body includes the first layered member and the secondlayered member. According to the sixtieth aspect of the presentinvention, it is possible to further effectively save weight of thebicycle sprocket because the layered structure extends from the sprocketteeth to the sprocket body.

In accordance with a sixty-first aspect of the present invention, thebicycle sprocket according to the thirty-fourth aspect is configured sothat the sprocket body has an axially projecting portion and an axiallyrecessed portion. The axially projecting portion and the axiallyrecessed portion are positioned at the sprocket body. According to thesixty-first aspect of the present invention, it is possible to providebicycle sprockets which are easily attached to each other to form amultiple bicycle sprocket assembly.

In accordance with a sixty-second aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the fifty-eighth aspect.The axially projecting portion of one of the bicycle sprockets mateswith the axially recessed portion of an adjacent one of the bicyclesprockets adjacent to the one of the bicycle sprockets while the bicyclesprockets are attached to each other. According to the sixty-secondaspect of the present invention, it is possible to provide a multiplebicycle sprocket assembly which is lightweight and has sufficientrigidity.

In accordance with a sixty-third aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the thirty-fourthaspect, and a sprocket support member to which the bicycle sprockets aremounted. According to the sixty-third aspect of the present invention,it is possible to provide a multiple bicycle sprocket assembly which islightweight and has sufficient rigidity.

In accordance with a sixty-fourth aspect of the present invention, themultiple sprocket assembly according to the sixty-third aspect isconfigured so that the sprocket support member has a unitary one-piecestructure. According to the sixty-fourth aspect of the presentinvention, it is possible to provide a multiple bicycle sprocketassembly which is lightweight and has sufficient rigidity.

In accordance with a sixty-fifth aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the sixtieth aspect. Theaxially projecting portion of one of the bicycle sprockets mates withthe axially recessed portion of an adjacent one of the bicycle sprocketsadjacent to the one of the bicycle sprockets while the bicycle sprocketsare attached to each other. According to the sixty-fourth aspect of thepresent invention, it is possible to provide a multiple bicycle sprocketassembly which is lightweight and has sufficient rigidity.

In accordance with a sixty-sixth aspect of the present invention, abicycle sprocket is provided that basically includes a sprocket body,and a plurality of sprocket teeth. The sprocket body has a rotationalaxis. The sprocket teeth extend radially outwardly from an outerperiphery of the sprocket body. At least one of the sprocket teethincluding a first layered member and a second layered member. The firstlayered member has a first axial surface and a second axial surfaceopposite to the first axial surface. The second layered member has athird axial surface and a fourth axial surface opposite to the thirdaxial surface. The third axial surface of the second layered member isattached to the first axial surface of the first layered member suchthat the first and second layered members overlap each other in an axialdirection as viewed parallel to the rotational axis and such that thesecond axial surface of the first layered member and the fourth axialsurface of the second layered member are exposed. The first layeredmember has a specific gravity that is less than that of the secondlayered member. According to the sixty-sixth aspect of the presentinvention, it is possible to effectively save weight of the bicyclesprocket while maintaining necessary rigidity.

In accordance with a sixty-seventh aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat each of the first and second layered members has an axial thicknessmore than or equal to 0.1 mm. According to the sixty-seventh aspect ofthe present invention, it is possible to effectively obtain necessaryrigidity of each of the first and second layered members.

In accordance with a sixty-eighth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first and second layered members do not overlap each other in aradial direction as viewed perpendicularly to the rotational axis.According to the sixty-eighth aspect of the present invention, it ispossible to effectively save weight of the bicycle sprocket whilemaintaining necessary rigidity.

In accordance with a sixty-ninth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the sprocket body includes the first layered member and the secondlayered member. According to the sixty-ninth aspect of the presentinvention, it is possible to further effectively save weight of thebicycle sprocket because the layered structure extends from the sprocketteeth to the sprocket body.

In accordance with a seventieth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the at least one of the sprocket teeth further includes a coatinglayer formed on a radially end surface of the first layered member.According to the seventieth aspect of the present invention, it ispossible to improve wear resistance of the first layered member.

In accordance with a seventy-first aspect of the present invention, thebicycle sprocket according to the seventieth aspect is configured sothat the coating layer is an intermetallic compound layer. According tothe seventy-first aspect of the present invention, it is possible toeffectively improve wear resistance of the first layered member.

In accordance with a seventy-second aspect of the present invention, thebicycle sprocket according to the seventy-first aspect is configured sothat the intermetallic compound layer is made of aluminum, and one ofnickel and iron. According to the seventy-second aspect of the presentinvention, it is possible to effectively improve wear resistance of thefirst layered member.

In accordance with a seventy-third aspect of the present invention, thebicycle sprocket according to the seventieth aspect is configured sothat the coating layer is a plated layer. According to the seventy-thirdaspect of the present invention, it is possible to effectively improvewear resistance of the first layered member.

In accordance with a seventy-fourth aspect of the present invention, thebicycle sprocket according to the seventy-third aspect is configured sothat the coating layer is a nickel-plated layer. According to theseventy-fourth aspect of the present invention, it is possible toeffectively improve wear resistance of the first layered member.

In accordance with a seventy-fifth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.According to the seventy-fifth aspect of the present invention, it ispossible to effectively save weight of the bicycle sprocket because ofsuch light weight metallic materials.

In accordance with a seventy-sixth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the second layered member is made of iron. According to theseventy-sixth aspect of the present invention, it is possible toeffectively obtain necessary rigidity of the bicycle sprocket because ofhigh rigidity of iron.

In accordance with a seventy-seventh aspect of the present invention,the bicycle sprocket according to the seventy-sixth aspect is configuredso that the second layered member is made of stainless steel. Accordingto the seventy-seventh aspect of the present invention, it is possibleto effectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel while obtaining necessary rigidity ofthe bicycle sprocket because of high rigidity of steel.

In accordance with a seventy-eighth aspect of the present invention, thebicycle sprocket according to the seventy-seventh aspect is configuredso that the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.According to the seventy-fifth aspect of the present invention, it ispossible to effectively save weight of the bicycle sprocket because ofsuch light weight metallic materials.

In accordance with a seventy-ninth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first layered member is made of non-metallic material.According to the seventy-ninth aspect of the present invention, it ispossible to select lightweight materials to realize further save weightof the bicycle sprocket.

In accordance with an eightieth aspect of the present invention, thebicycle sprocket according to the seventy-ninth aspect is configured sothat the non-metallic material of the first layered member includesresin. According to the eightieth aspect of the present invention, it ispossible to select lightweight materials to realize further save weightof the bicycle sprocket because of resin.

In accordance with an eighty-first aspect of the present invention, thebicycle sprocket according to the eightieth aspect is configured so thatthe non-metallic material of the first layered member isfiber-reinforced material. According to the eighty-first aspect of thepresent invention, because of the fiber-reinforced material, it ispossible to select lightweight materials to realize further save weightof the bicycle sprocket while maintaining necessary rigidity.

In accordance with an eighty-second aspect of the present invention, thebicycle sprocket according to the seventy-ninth aspect is configured sothat the second layered member is made of iron. According to theeighty-second aspect of the present invention, it is possible toeffectively obtain necessary rigidity of the bicycle sprocket because ofhigh rigidity of iron.

In accordance with an eighty-third aspect of the present invention, thebicycle sprocket according to the eighty-second aspect is configured sothat the second layered member is made of stainless steel. According tothe eighty-third aspect of the present invention, it is possible toeffectively prevent rust of the bicycle sprocket because ofcharacteristic of stainless steel while obtaining necessary rigidity ofthe bicycle sprocket because of high rigidity of steel.

In accordance with an eighty-fourth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first layered member and the second layered member are attachedto each other by diffusion bonding. According to the fiftieth aspect ofthe present invention, it is possible to firmly attach the secondlayered member to the first layered member.

In accordance with an eighty-fifth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first layered member and the second layered member are attachedto each other with an adhesive. According to the eighty-fifth aspect ofthe present invention, it is possible to inexpensively attach the secondlayered member to the first layered member.

In accordance with an eighty-sixth aspect of the present invention, thebicycle sprocket according to the eightieth aspect is configured so thatthe first layered member and the second layered member are attached toeach other by an integral molding process. According to the eighty-sixthaspect of the present invention, it is possible to effectively andquickly manufacture the bicycle sprockets.

In accordance with an eighty-seventh aspect of the present invention,the bicycle sprocket according to the seventy-seventh aspect isconfigured so that the second layered member has Vickers hardness largerthan or equal to 400 (HV). According to the eighty-seventh aspect of thepresent invention, it is possible to effectively obtain necessaryrigidity of the second layered member.

In accordance with an eighty-eighth aspect of the present invention, thebicycle sprocket according to the seventy-fifth aspect is configured sothat the first layered member is made of quenched aluminum. According tothe eighty-eighth aspect of the present invention, it is possible toeffectively improve rigidity of the first layered member.

In accordance with an eighty-ninth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the plurality of sprocket teeth includes the first layered memberand the second layered member. According to the eighty-ninth aspect ofthe present invention, it is possible to further save weight of thebicycle sprocket while maintaining necessary rigidity.

In accordance with a ninetieth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the first layered member extends radially inwardly from an innerperiphery of the sprocket body, and the first layered member has anaxially projecting portion and an axially recessed portion. The axiallyprojecting portion and the axially recessed portion are positionedradially inwardly from the inner periphery of the sprocket body.According to the ninetieth aspect of the present invention, it ispossible to provide bicycle sprockets which are easily attached to eachother to form a multiple bicycle sprocket assembly.

In accordance with a ninety-first aspect of the present invention, thebicycle sprocket according to the ninetieth aspect is configured so thatthe first layered member has a bicycle hub engaging profile at alocation of a radially inner end of the first layered member. Accordingto the ninety-first aspect of the present invention, it is possible toprovide a multiple rear sprocket assembly which is lightweight and hassufficient rigidity.

In accordance with a ninety-second aspect of the present invention, thebicycle sprocket according to the ninetieth aspect is configured so thatthe sprocket body includes the first layered member and the secondlayered member. According to the ninety-second aspect of the presentinvention, it is possible to further effectively save weight of thebicycle sprocket because the layered structure extends from the sprocketteeth to the sprocket body.

In accordance with a ninety-third aspect of the present invention, thebicycle sprocket according to the ninety-first aspect is configured sothat the sprocket body includes the first layered member and the secondlayered member. According to the ninety-third aspect of the presentinvention, it is possible to further effectively save weight of thebicycle sprocket because the layered structure extends from the sprocketteeth to the sprocket body.

In accordance with a ninety-fourth aspect of the present invention, thebicycle sprocket according to the sixty-sixth aspect is configured sothat the sprocket body has an axially projecting portion and an axiallyrecessed portion. The axially projecting portion and the axiallyrecessed portion are positioned at the sprocket body. According to theninety-fourth aspect of the present invention, it is possible to providebicycle sprockets which are easily attached to each other to form amultiple bicycle sprocket assembly.

In accordance with a ninety-fifth aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the ninetieth aspect.The axially projecting portion of one of the bicycle sprockets mateswith the axially recessed portion of an adjacent one of the bicyclesprockets adjacent to the one of the bicycle sprockets while the bicyclesprockets are attached to each other. According to the ninety-fifthaspect of the present invention, it is possible to provide a multiplebicycle sprocket assembly which is lightweight and has sufficientrigidity.

In accordance with a ninety-sixth aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the sixty-sixth aspect,and a sprocket support member to which the bicycle sprockets aremounted. According to the ninety-sixth aspect of the present invention,it is possible to provide a multiple bicycle sprocket assembly which islightweight and has sufficient rigidity.

In accordance with a ninety-seventh aspect of the present invention, themultiple sprocket assembly according to the ninety-sixth aspect isconfigured so that the sprocket support member has a unitary one-piecestructure. According to the ninety-seventh aspect of the presentinvention, it is possible to provide a multiple bicycle sprocketassembly which is lightweight and has sufficient rigidity.

In accordance with a ninety-eighth aspect of the present invention, amultiple sprocket assembly is provided that basically includes aplurality of the bicycle sprockets according to the ninety-fourthaspect. The axially projecting portion of one of the bicycle sprocketsmates with the axially recessed portion of an adjacent one of thebicycle sprockets adjacent to the one of the bicycle sprockets while thebicycle sprockets are attached to each other. According to theninety-eighth aspect of the present invention, it is possible to providea multiple bicycle sprocket assembly which is lightweight and hassufficient rigidity.

Other objects, features, aspects and advantages of the disclosed bicyclecomponent operating apparatus will become apparent to those skilled inthe art from the following detailed description, which, taken inconjunction with the annexed drawings, discloses one embodiment of thebicycle component operating apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a side elevational view of a bicycle having a bicycle sprocketin accordance with a first embodiment;

FIG. 2 is a perspective view of the bicycle sprocket of the bicycleillustrated in FIG. 1;

FIG. 3 is an enlarged, partial cross sectional view of the bicyclesprocket illustrated in FIG. 2;

FIG. 4 is a perspective view of a pair of bicycle sprockets inaccordance with a second embodiment, the bicycle sprockets detachablycoupled to each other;

FIG. 5 is an exploded perspective view of the bicycle sprocketsillustrated in FIG. 4;

FIG. 6 is a perspective view of one of the bicycle sprockets illustratedin FIG. 4;

FIG. 7 is an enlarged, partial cross sectional view of the bicyclesprockets illustrated in FIG. 4;

FIG. 8 is an enlarged, partial cross sectional view of the bicyclesprockets illustrated in FIG. 4;

FIG. 9 is an enlarged, partial cross sectional view of a pair ofmodified bicycle sprockets in accordance with the second embodiment, thebicycle sprockets detachably coupled to each other;

FIG. 10 is a perspective view of a pair of modified bicycle sprockets inaccordance with the second embodiment, the bicycle sprocketsnon-detachably coupled to each other;

FIG. 11 is a cross sectional view of the bicycle sprockets illustratedin FIG. 10;

FIG. 12 is an outside elevational view of a bicycle sprocket inaccordance with a third embodiment;

FIG. 13 is an inside elevational view of the bicycle sprocketillustrated in FIG. 12;

FIG. 14 is a second layered member of the bicycle sprocket illustratedin FIG. 12;

FIG. 15 is an enlarged, partial cross sectional view of the bicyclesprocket illustrated in FIG. 12;

FIG. 16 is a perspective view of a bicycle sprocket in accordance with afourth embodiment;

FIG. 17 is an inside elevational view of the bicycle sprocketillustrated in FIG. 16;

FIG. 18A is an enlarged, partial cross sectional view of the bicyclesprocket illustrated in FIG. 16;

FIG. 18B is an enlarged, partial cross sectional view of the bicyclesprocket illustrated in FIG. 16, with the bicycle sprocket detachablycoupled to an adjacent sprocket;

FIG. 19 is a perspective view of a bicycle sprocket in accordance with afifth embodiment;

FIG. 20 is an inside elevational view of the bicycle sprocketillustrated in FIG. 19;

FIG. 21 is an enlarged, partial cross sectional view of the bicyclesprocket illustrated in FIG. 19;

FIG. 22 is a perspective view of a bicycle sprocket in accordance with asixth embodiment;

FIG. 23 is an inside elevational view of the bicycle sprocketillustrated in FIG. 22;

FIG. 24 is a perspective view of a bicycle sprocket in accordance with aseventh embodiment;

FIG. 25 is an inside elevational view of the bicycle sprocketillustrated in FIG. 24; and

FIG. 26 is an enlarged, partial perspective view of the bicycle sprocketillustrated in FIG. 24.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the art from thisdisclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

Referring initially to FIG. 1, a bicycle 10 is illustrated having a rearbicycle hub 11 with a multi-stage rear sprocket assembly (cassette) 12(e.g., a multiple sprocket assembly) in accordance with a firstembodiment. While the bicycle 10 is illustrated as a road bike, it willbe apparent to those skilled in the art from this disclosure that thepresent invention can be applied to other types of bicycles such as amountain bike. The rear sprocket assembly 12 includes ten (10) rearsprockets S (e.g., a plurality of bicycle sprockets) that are mounted onthe rear bicycle hub 11 with a plurality of spacers (or sprocket supportmembers) arranged between the sprockets S. An innermost sprocket S ofthe rear sprocket assembly 12 is the largest, and has the most teeth,while an outermost sprocket S of the rear sprocket assembly 12 is thesmallest, and has the fewest teeth. In the illustrated embodiment, thesprockets S have 34T, 30T, 26T, 23T, 21T, 19T, 17T, 15T, 13T, 1 IT toothconfigurations, respectively. However, it will be apparent to thoseskilled in the bicycle art from this disclosure that the sprockets S canhave different tooth configurations as needed and/or desired.Furthermore, it will be apparent to those skilled in the bicycle artfrom this disclosure that the rear sprocket assembly 12 can includedifferent number of the sprockets S, such as less than or more than tenas needed and/or desired.

Referring to FIG. 1, the bicycle 10 basically has a frame 14 with frontand rear wheels 15 and 16 rotatably coupled thereto. A front fork 17 ispivotally coupled to the front of the frame 14 with the front wheel 15rotatably coupled thereto in a conventional manner. A handlebar 18 isrigidly attached to the front fork 17 in order to turn the front wheel15 to steer the bicycle 10. The rear wheel 16 is rotatably coupled to arear portion or rear triangle of the frame 14 via the rear bicycle hub11 in a conventional manner. A seat 19 is adjustably coupled to theframe 14 via a seat post in a conventional manner, and a drive train 20is provided on the bicycle 10 for propelling the bicycle 10. The bicycle10 is conventional except for selected parts of the drive train 20, asdiscussed below.

The drive train 20 basically includes the rear multi-stage sprocketassembly 12, a pair of pedals 21, a front multi-stage sprocket assembly22 mounted to rotate with the pedals 21, and a chain 23 extendingbetween the rear multi-stage sprocket assembly 12 and the frontmulti-stage sprocket assembly 22. The rear sprocket assembly 12 ispreferably coupled to the rear bicycle hub 11 via a freewheel. Thepedals 21 are coupled to the front multi-stage sprocket assembly 22 by aconventional crank set to transfer force from the rider to the chain 23.The force from the chain 23 is selectively transferred to the rear wheel16 via the rear bicycle hub 11 (e.g. via the rear sprocket assembly 12depending on the direction of rotation) in a conventional manner. Thechain 23 used in the drive train 20 is designed to be compatible withthe rear ten-stage sprocket assembly 12. In particular, the chain 23 isa conventional chain used with a conventional rear sprocket assembly.Accordingly, the chain 23 will not be explained and/or illustrated indetail herein. Similarly, the front sprocket assembly 22 is configuredto be compatible with the chain 23. Such front sprocket assembly 22 iswell known in the bicycle art. Accordingly, the front sprocket assembly22 will not be explained and/or illustrated in detail herein.Nevertheless, it will be apparent to those skilled in the art from thisdisclosure that the present invention can be applied to such a frontsprocket assembly.

The drive train 20 is basically controlled by conventional front andrear shifting units (not shown) that control the lateral positions offront and rear derailleurs 27 and 28 in a conventional manner. Thus,when the rider is pedaling, the front and rear sprocket assemblies 22and 12 are rotating to circulate or cycle the chain 23 due to themovement of the pedals 21. The shifting units (not shown) can beactuated by the rider to control the lateral positions of the frontand/or rear derailleurs 27 and/or 28. When the chain 23 is circulated orcycled in the forward (clockwise direction as seen in FIG. 1), theshifting units can be actuated to control the gear ratio of the drivetrain 20 by controlling the lateral position of the chain 23 via thederailleurs 27 and 28 in a conventional manner. The derailleurs 27 and28 selectively apply a lateral force inwardly/outwardly to the chain 23to cause up/down shifts in a conventional manner. The drive train 20 isbasically conventional, except for the rear multi-stage sprocketassembly 12 in the embodiment. Thus, the drive train 20 will not bediscussed and/or illustrated in further detail herein, except as relatedto the rear multi-stage sprocket assembly 12.

Since the various parts of the bicycle 10 and most of the parts of thedrive train 20 are well known in the bicycle art, these parts of thebicycle 10 and the drive train 20 will not be discussed and/orillustrated in detail herein, except as related to the presentinvention. However, it will be apparent to those skilled in the bicycleart from this disclosure that various conventional bicycle parts such asbrakes, different hub structures, etc., which are not illustrated and/ordiscussed in detail herein, can be used in conjunction with the presentinvention as needed and/or desired.

Referring now to FIGS. 2 and 3, the sprockets S of the rear sprocketassembly 12 will now be explained in more detail. As mentioned above,the rear sprocket assembly 12 includes ten (10) rear sprockets S thatare mounted on the rear bicycle hub 11 with the spacers arranged betweenthe sprockets S such that the sprockets S are spaced from each other atpredetermined intervals. The spacers can have any conventionalconfiguration as needed and/or desired. For example, the spacers can beeach formed as a one-piece, unitary member that is made of suitablerigid and/or lightweight materials. For example, the spacers can be madeof rigid resin materials or lightweight metallic materials such asaluminum. Since the spacers can be conventional, the spacers will not bediscussed in detail herein. The sprockets S and the spacers are fixedlymounted on the rear bicycle hub 11 such that the sprockets S rotatetogether about a center hub rotation axis of the rear bicycle hub 11.The sprockets S typically rotate together in a forward rotationaldirection (e.g., in a clockwise direction as viewed in FIG. 1) when therider is pedaling in a forward (clockwise) direction to propel thebicycle 10 in a forward direction as seen in FIG. 1.

In the illustrated embodiment, one of the sprockets S has amulti-layered structure as described below. Specifically, in theillustrated embodiment, as shown in FIG. 2, the largest one of thesprockets S (hereinafter merely referred as a “largest sprocket S” or“sprocket S”) has the multi-layered structure. Of course, any one(s) ofthe sprockets S can have this multi-layered structure. However, in theillustrated embodiment, the other sprockets S other than the largestsprocket S have any conventional configuration as needed and/or desired.For example, these sprockets S other than the largest sprockets S can beeach formed as a one-piece, unitary member from a metallic material thatis suitable for a bicycle sprocket such as an iron or an iron alloy.Therefore, in the illustrated embodiment, the following disclosure willfocus on the configuration of the largest sprocket S for the sake ofbrevity.

As shown in FIG. 2, the sprocket S (e.g., a bicycle sprocket) basicallyincludes a sprocket body 32, and a plurality of sprocket teeth 34. Thesprocket body 32 has a rotational axis X1. The sprocket body 32 includesan outer periphery 36 and an inner periphery 38. The sprocket S isradially straight as the sprocket S extends between the outer periphery36 and the inner periphery 38. In other words, the sprocket S isgenerally a flat plate with opposite sprocket side surfaces being planarbetween the outer periphery 36 and the inner periphery 38 other thanvarious holes and recesses. The inner periphery 38 defines an opening 38a that is free of any freewheel engaging splines. In the illustratedembodiment, the sprocket body 32 includes a plurality of fastener holes40 for receiving outer rivets for fastening the sprocket S to thespacer. The sprocket teeth 34 extend radially outwardly from the outerperiphery 36 of the sprocket body 32. In the illustrated embodiment, thesprocket body 32 is defined as a part of the sprocket S that is radiallyinwardly disposed with respect to an imaginary circle C connectinginnermost positions of gaps circumferentially disposed between thesprocket teeth 34. As mentioned above, the sprocket S is larger than anyother sprocket of the rear sprocket assembly 12. Since the sprocket S isthe largest sprocket of the rear sprocket assembly 12, the total numberof the sprocket teeth 34 is typically greater than the other sprocketsof the rear sprocket assembly 12. In the illustrated embodiment, asshown in FIG. 2, the total number of the sprocket teeth 34 isthirty-four. Of course, the total number of the sprocket teeth 34 can belarger or smaller than thirty-four as needed and/or desired.

In the illustrated embodiment, as shown in FIG. 3, the sprocket Sincludes a first layered member 42, a second layered member 44, a thirdlayered member 46, and a coating layer 48. In the illustratedembodiment, the first, second and third layered members 42, 44 and 46radially outwardly extends from the inner periphery 38 of the sprocketbody 32 to the sprocket teeth 34. Thus, in the illustrated embodiment,the plurality (e.g., all) of the sprocket teeth 34 includes the firstlayered member 42 and the second layered member 44. In the illustratedembodiment, the plurality of the sprocket teeth 34 further includes thethird layered member 46. Furthermore, the plurality of the sprocketteeth 34 includes the coating layer 48. Alternatively or optionally, atleast one (e.g., not all) of the sprocket teeth 34 can include the firstlayered member 42 and the second layered member 44. The at least one ofthe sprocket teeth 34 can also include the third layered member 46.Furthermore, the at least one of the sprocket teeth 34 can also includethe coating layer 48. On the other hand, in the illustrated embodiment,the sprocket body 32 includes the first layered member 42 and the secondlayered member 44. Furthermore, the sprocket body 32 includes the thirdlayered member 46. Specifically, in the illustrated embodiment, thefirst, second and third layered members 42, 44 and 46 radially extendbetween the inner periphery 38 of the sprocket body 32 and the outerperiphery 36 of the sprocket body 32 other than various holes andrecesses.

As shown in FIG. 2, the first layered member 42 has a first axialsurface 52 and a second axial surface 54 opposite to the first axialsurface 52 with respect to the rotational axis X1. The second layeredmember 44 is attached to the first axial surface 52 of the first layeredmember 42. The third layered member 46 is attached to the second axialsurface 54 of the first layered member 42. The coating layer 48 isformed on a radially end surface 56 of the first layered member 42. Inthe illustrated embodiment, the first, second and third layered members42, 44 and 46 are flat layered members. Thus, the first and secondlayered members 42 and 44 overlap each other in an axial direction asviewed parallel to the rotational axis X1, while the first and secondlayered members 42 and 44 do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis X1.Furthermore, the first and third layered members 42 and 46 overlap eachother in the axial direction as viewed parallel to the rotational axisX1, while the first and third layered members 42 and 46 do not overlapeach other in the radial direction as viewed perpendicularly to therotational axis X1. In the illustrated embodiment, the first layeredmember 42 is axially disposed between the second and third layeredmembers 44 and 46 such that the first layered member 42 is axiallycompletely covered by the second and third layered members 44 and 46.Furthermore, the first layered member 42 is radially inwardly disposedrelative to the coating layer 48 such that the radially end surface 56of the first layered member 42 is radially completely covered by thecoating layer 48. However, alternatively, the first layered member 42can be partially exposed through the second and third layered members 44and 46 in the axial direction, while the first layered member 42 can bepartially exposed through the coating layer 48 in the radial direction.The coating layer 48 can be omitted as needed and/or desired so that thefirst layered member can be radially exposed and/or has the same outercontour as those of the second and third layered members.

The first layered member 42 has an axial thickness more than or equal to0.1 mm. The first layered member 42 has a specific gravity that is lessthan that of the second layered member 44. Furthermore, in theillustrated embodiment, the first layered member 42 has a specificgravity that is less than that of the third layered member 46. The firstlayered member 42 is made of a material selected from the groupconsisting of aluminum, titanium, magnesium and beryllium. Specifically,in the illustrated embodiment, the first layered member 42 is made ofquenched aluminum. However, alternatively, the first layered member 42can be made of non-metallic material. Specifically, the non-metallicmaterial of the first layered member 42 can includes resin. For example,the first layered member 42 can be made of hard plastic resin.Alternatively, the non-metallic material of the first layered member 42can be fiber-reinforced material. For example, the first layered member42 can be made of a carbon fiber-reinforced plastic or polymer (FRP).

The second layered member 44 has an axial thickness more than or equalto 0.1 mm. The second layered member 44 is made of metallic material.Specifically, in the illustrated embodiment, the second layered member44 is made of iron. Of course, the second layered member 44 can be madeof other metallic material. For example, the second layered member 44can be made of stainless steel. In the illustrated embodiment, thesecond layered member 44 has a specific gravity that is equal to that ofthe third layered member 46. Specifically, in the illustratedembodiment, the second and third layered members 44 and 46 are made ofthe same material. However, of course, the second and third layeredmembers 44 and 46 can be made of different materials as needed and/ordesired. The second layered member 44 preferably has Vickers hardnesslarger than or equal to 400 (HV). The second layered member 44 isfixedly attached to the first layered member 42 by a suitable fixingmanner. Specifically, in the illustrated embodiment, the first layeredmember 42 and the second layered member 44 are attached to each other bydiffusion bonding. However, alternatively, the first layered member 42and the second layered member 44 can be attached to each other with anadhesive. Furthermore, the first layered member 42 and the secondlayered member 44 can be attached to each other by an integral moldingprocess. Specifically, when the first layered member 42 is made ofmetallic material, the first and second layered members 42 and 44 can beattached to each other by forming a clad structure. Furthermore, whenthe first layered member 42 is made of resin material, the first andsecond layered members 42 and 44 can be attached to each other by theintegral molding process. In particular, the integral molding processcan be performed such that the resin of the first layered member 42 canextend into dimples of the second layered member 44 during formation ofthe first layered member 42. In the illustrated embodiment, with thisintegral molding process, the first layered member 42, which is made ofresin, is molded while simultaneously attaching the first layered member42 to the second layered member 44, which includes dimples for receivingthe resin.

The third layered member 46 has an axial thickness more than or equal to0.1 mm. The third layered member 46 is made of metallic material.Specifically, in the illustrated embodiment, the third layered member 46is made of iron. Of course, the third layered member 46 can be made ofother metallic material. For example, the third layered member 46 can bemade of stainless steel. The third layered member 46 preferably hasVickers hardness larger than or equal to 400 (HV). The third layeredmember 46 is fixedly attached to the first layered member 42 by asuitable fixing manner. Specifically, in the illustrated embodiment, thefirst layered member 42 and the third layered member 46 are attached toeach other by diffusion bonding. However, alternatively, the firstlayered member 42 and the third layered member 46 can be attached toeach other with an adhesive. Furthermore, the first layered member 42and the third layered member 46 can be attached to each other by anintegral molding process. Specifically, when the first layered member 42is made of metallic material, the first and third layered members 42 and46 can be attached to each other by forming a clad structure.Furthermore, when the first layered member 42 is made of resin material,the first and third layered members 42 and 46 can be attached to eachother by the integral molding process. In particular, the integralmolding process can be performed such that the resin of the firstlayered member 42 can extend into dimples of the third layered member 46during formation of the first layered member 42. In the illustratedembodiment, with this integral molding process, the first layered member42, which is made of resin, is molded while simultaneously attaching thefirst layered member 42 to the third layered member 46, which includesdimples for receiving the resin.

As shown in FIG. 3, the coating layer 48 is preferably formed on theradially end surface 56 of the first layered member 42. Specifically, inthe illustrated embodiment, the coating layer 48 circumferentiallyextends along the radially end surface 56 of the first layered member 42about the rotation axis X1. In the illustrated embodiment, the coatinglayer 48 is disposed axially between the second and third layeredmembers 44 and 46 such that an radially end surface 48 a of the coatinglayer 48 can be flush with radially end surfaces 44 a and 46 a of thesecond and third layered members 44 and 46. In other words, in thiscase, the first layered member 42 has the outermost diameter of thefirst layered member 42 that is smaller than those of the second andthird layered members 44 and 46 such that the second and third layeredmembers 44 and 46 defines an circumferential groove for receiving thecoating layer 48 therebetween. Alternatively, the coating layer 48 canbe formed on an radially end surface of the sprocket teeth 34 that isformed by the radially end surfaces 56, 44 a and 46 a of the first,second and third layered members 42, 44 and 46. In this case, the first,second and third layered members 42, 44 and 46 have the same outermostdiameter. In the illustrated embodiment, the coating layer 48 is anintermetallic compound layer. Specifically, the intermetallic compoundlayer of the coating layer 48 is made of aluminum, and one of nickel andiron. In particular, in the illustrated embodiment, the coating layer 48is plated layer. More specifically, the coating layer 48 is anickel-plated layer. In the illustrated embodiment, the coating layer 48is formed on the radially end surface 56 of the first layered member 42such that the coating layer 48 protect the first layered member 42 frombeing wore away by the chain 23. The coating layer 48 can also be formedon the radially end surface 56 of the first layered member 42 in aconventional manner.

In the illustrated embodiment, the sprocket S includes the first layeredmember 42, the second layered member 44, the third layered member 46,and the coating layer 48. Thus, sprocket teeth 34 that contact with thechain 23 are all covered by metallic materials, which results inensuring strength, rigidity, and abrasion resistance. On the other hand,the first layered member 42 is made from a material having a smallerspecific gravity than the second and third layered members 44 and 46,which results in reducing the weight of the sprocket S. However, themulti-layered structure of the sprocket S is not limited to this. Thesprocket S can only include the first layered member 42, the secondlayered member 44 and the coating layer 48 without the third layeredmember 46. The sprocket S can only include the first layered member 42,the third layered member 46 and the coating layer 48 without the secondlayered member 44. Furthermore, the sprocket S can only include thefirst layered member 42, the second layered member 44 and the thirdlayered member 46 without the coating layer 48.

In the illustrated embodiment, the sprocket S is the largest sprocket ofthe rear sprocket assembly 12. However, any one(s) of the sprockets S ofthe rear sprocket assembly 12 can include the same configuration as thesprocket S illustrated in FIG. 2. Moreover, any one(s) of chain wheelsor front sprocket of the front sprocket assembly 22 (FIG. 1) can alsoinclude the same configuration as the sprocket S illustrated in FIG. 2.

Second Embodiment

Referring now to FIGS. 4 to 8, a rear sprocket assembly 112 (e.g., amultiple sprocket assembly) in accordance with a second embodiment willnow be explained. The rear sprocket assembly 112 is basically identicalto the rear sprocket assembly 12 in accordance with the firstembodiment, except that a plurality of sprockets of the rear sprocketassembly 112 includes a pair of rear sprockets Sa and Sb (e.g., aplurality of bicycle sprockets) detachably coupled to each other, asexplained below.

In view of the similarity between the first and second embodiments, theparts of the second embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this second embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“100” added thereto. In any event, the descriptions of the parts of thesecond embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis second embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, the sprockets Sa and Sb havemulti-layered structures, respectively, as described below.Specifically, in the illustrated embodiment, as shown in FIGS. 4 and 5,the sprocket Sa is the largest sprocket of the rear sprocket assembly112, while the sprocket Sb is the second largest sprocket of the rearsprocket assembly 112. Of course, any one of adjacent pairs of thesprockets of the rear sprocket assembly 112 can have this multi-layeredstructure. However, in the illustrated embodiment, the other sprocketsother than the sprockets Sa and Sb have any conventional configurationas needed and/or desired. For example, these sprockets other than thesprockets Sa and Sb can be each formed as a one-piece, unitary memberfrom a metallic material that is suitable for a bicycle sprocket such asan iron or an iron alloy. Therefore, in the illustrated embodiment, thefollowing disclosure will focus on the configuration of the sprockets Saand Sb for the sake of brevity.

As shown in FIG. 4, the sprocket Sa (e.g., a bicycle sprocket) basicallyincludes a sprocket body 132 a, and a plurality of sprocket teeth 134 a.The sprocket body 132 a has a rotational axis X1. The sprocket body 132a includes an outer periphery 136 a and an inner periphery 138 a. Thesprocket teeth 134 a extend radially outwardly from the outer periphery136 a of the sprocket body 132 a. On the other hand, the sprocket Sb(e.g., a bicycle sprocket) basically includes a sprocket body 132 b, anda plurality of sprocket teeth 134 b. The sprocket body 132 b has therotational axis X1. The sprocket body 132 b includes an outer periphery136 b and an inner periphery 138 b. The sprocket teeth 134 b extendradially outwardly from the outer periphery 136 b of the sprocket body132 b. In the illustrated embodiment, the sprocket Sa is the largestsprocket of the rear sprocket assembly 112. As shown in FIGS. 4 and 5,the total number of the sprocket teeth 134 a is thirty-four. On theother hand, in the illustrated embodiment, the sprocket Sb is the secondlargest sprocket of the rear sprocket assembly 112. As shown in FIGS. 4and 5, the total number of the sprocket teeth 134 b is thirty. Ofcourse, the total numbers of the sprocket teeth 134 a and 134 b can bedifferent numbers as needed and/or desired.

In the illustrated embodiment, the sprockets Sa and Sb havemulti-layered structures, respectively. Specifically, as shown in FIGS.5, 7 and 8, the sprocket Sa includes a first layered member 142 a, asecond layered member 144 a, a third layered member 146 a, and a coatinglayer 148 a. In the illustrated embodiment, the first, second and thirdlayered members 142 a, 144 a and 146 a radially outwardly extends fromthe inner periphery 138 a of the sprocket body 132 a to the sprocketteeth 134 a. Furthermore, as shown in FIGS. 5, 7 and 8, the sprocket Sbincludes a first layered member 142 b, a second layered member 144 b, athird layered member 146 b, and a coating layer 148 b. In theillustrated embodiment, the first, second and third layered members 142b, 144 b and 146 b radially outwardly extends from the inner periphery138 b of the sprocket body 132 b to the sprocket teeth 134 b. Themulti-layered structures of the sprockets Sa and Sb are basicallyidentical to that of the sprocket S in accordance with the firstembodiment, except that the first layered members 142 a and 142 b extendradially inwardly from the inner peripheries 138 a and 138 b of thesprocket bodies 132 a and 132 b, respectively. Furthermore, the firstlayered members 142 a and 142 b, the second layered members 144 a and144 b, the third layered members 146 a and 146 b, and the coating layers148 a and 148 b can be made of the same material as the first layeredmember 42, the second layered member 44, the third layered member 146,and the coating layer 48 in accordance with the first embodiment,respectively. Furthermore, the first, second and third layered members142 a, 144 a and 146 a and the coating layer 148 a are attached withrespect to each other in the same fixing manner as discussed in thefirst embodiment, while the first, second and third layered members 142b, 144 b and 146 b and the coating layer 148 b are attached with respectto each other in the same fixing manner as discussed in the firstembodiment. Thus, the detailed description of the multi-layeredstructures of the sprockets Sa and Sb will be omitted for the sake ofbrevity. It will be apparent to those skilled in the art from thisdisclosure that the descriptions and illustrations of the parts ofsprocket S in accordance with the first embodiment also apply to theparts of the sprockets Sa and Sb having the same name, except asdiscussed and/or illustrated herein.

As shown in FIGS. 7 and 8, in regards to the sprocket Sa, the firstlayered member 142 a has a first axial surface 152 a and a second axialsurface 154 a opposite to the first axial surface 152 a with respect tothe rotational axis X1. The second layered member 144 a is attached tothe first axial surface 152 a of the first layered member 142 a. Thethird layered member 146 a is attached to the second axial surface 154 aof the first layered member 142 a. The coating layer 148 a is formed ona radially end surface 156 a of the first layered member 142 a. In theillustrated embodiment, the first, second and third layered members 142a, 144 a and 146 a are flat layered members at the sprocket body 132 aand the sprocket teeth 134 a. Thus, in regards to the sprocket body 132a and the sprocket teeth 134 a of the sprocket Sa, the first and secondlayered members 142 a and 144 a overlap each other in an axial directionas viewed parallel to the rotational axis X1, while the first and secondlayered members 142 a and 144 a do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis X1.Furthermore, in regards to the sprocket body 132 a and the sprocketteeth 134 a of the sprocket Sa, the first and third layered members 142a and 146 a overlap each other in the axial direction as viewed parallelto the rotational axis X1, while the first and third layered members 142a and 146 a do not overlap each other in the radial direction as viewedperpendicularly to the rotational axis X1. In the illustratedembodiment, the first layered member 142 a is axially disposed betweenthe second and third layered members 144 a and 146 a at the sprocketbody 132 a and the sprocket teeth 134 a such that the first layeredmember 142 a is axially completely covered by the second and thirdlayered members 144 a and 146 a at the sprocket body 132 a and thesprocket teeth 134 a. Furthermore, the first layered member 142 a isradially inwardly disposed relative to the coating layer 148 a such thatthe radially end surface 156 a of the first layered member 142 a isradially completely covered by the coating layer 148 a. However,alternatively, the first layered member 142 a can be partially exposedthrough the second and third layered members 144 a and 146 a in theaxial direction, while the first layered member 142 a can be partiallyexposed through the coating layer 148 a in the radial direction. In theillustrated embodiment, the first layered member 142 a has a specificgravity that is less than that of the second layered member 144 a.Furthermore, in the illustrated embodiment, the first layered member 142a has a specific gravity that is less than that of the third layeredmember 146 a.

Similarly, as shown in FIGS. 7 and 8, in regards to the sprocket Sb, thefirst layered member 142 b has a first axial surface 152 b and a secondaxial surface 154 b opposite to the first axial surface 152 b withrespect to the rotational axis X1. The second layered member 144 b isattached to the first axial surface 152 b of the first layered member142 b. The third layered member 146 b is attached to the second axialsurface 154 b of the first layered member 142 b. The coating layer 148 bis formed on a radially end surface 156 b of the first layered member142 b. In the illustrated embodiment, the first, second and thirdlayered members 142 b, 144 b and 146 b are flat layered members at thesprocket body 132 b and the sprocket teeth 134 b. Thus, in regards tothe sprocket body 132 b and the sprocket teeth 134 b of the sprocket Sb,the first and second layered members 142 b and 144 b overlap each otherin an axial direction as viewed parallel to the rotational axis X1,while the first and second layered members 142 b and 144 b do notoverlap each other in a radial direction as viewed perpendicularly tothe rotational axis X1. Furthermore, in regards to the sprocket body 132b and the sprocket teeth 134 b of the sprocket Sa, the first and thirdlayered members 142 b and 146 b overlap each other in the axialdirection as viewed parallel to the rotational axis X1, while the firstand third layered members 142 b and 146 b do not overlap each other inthe radial direction as viewed perpendicularly to the rotational axisX1. In the illustrated embodiment, the first layered member 142 b isaxially disposed between the second and third layered members 144 b and146 b at the sprocket body 132 b and the sprocket teeth 134 b such thatthe first layered member 142 b is axially completely covered by thesecond and third layered members 144 b and 146 b at the sprocket body132 b and the sprocket teeth 134 b. Furthermore, the first layeredmember 142 b is radially inwardly disposed relative to the coating layer148 b such that the radially end surface 156 b of the first layeredmember 142 b is radially completely covered by the coating layer 148 b.However, alternatively, the first layered member 142 b can be partiallyexposed through the second and third layered members 144 b and 146 b inthe axial direction, while the first layered member 142 b can bepartially exposed through the coating layer 148 b in the radialdirection. In the illustrated embodiment, the first layered member 142 bhas a specific gravity that is less than that of the second layeredmember 144 b. Furthermore, in the illustrated embodiment, the firstlayered member 142 b has a specific gravity that is less than that ofthe third layered member 146 b.

In the illustrated embodiment, as shown in FIGS. 5, 7 and 8, the firstlayered member 142 a of the sprocket Sa extends radially inwardly fromthe inner periphery 138 a of the sprocket body 132 a. Specifically, thefirst layered member 142 a of the sprocket Sa has a sprocket supportmember 162 a. In the illustrated embodiment, the sprocket support member162 a has a plurality of (e.g., six in this embodiment) sprocket arms163 a radially connecting the inner periphery 138 a of the first layeredmember 142 a to a center boss 164 a. Of course, it will be apparent tothose skilled in the art from this disclosure that the number of thesprocket arms 163 a can be more than or less than six as needed and/ordesired. Specifically, in the illustrated embodiment, each of thesprocket arms 163 a extends in a direction slanted relative to theradial direction of the rotational axis X1. The center boss 164 a has abicycle hub engaging profile 165 a on an inner peripheral surface of thecenter boss 164 a. In other words, the first layered member 142 a hasthe bicycle hub engaging profile 165 a at a location of a radially innerend of the sprocket support member 162 a of the first layered member 142a. The bicycle hub engaging profile 165 a defines a plurality ofengaging splines that is dimensioned to be non-rotatably engage withsplines of the freewheel (not shown) of the rear bicycle hub 11 in arelatively conventional manner. Preferably, the bicycle hub engagingprofile 165 a is configured so that the rear sprocket assembly 112 canonly fit on the freewheel in a single orientation.

As shown in FIGS. 5, 7 and 8, each of the sprocket arms 163 a of thefirst layered member 142 a has an axially projecting portion 166 a andan axially recessed portion 168 a. The axially projecting portions 166 aand the axially recessed portions 168 a are positioned radially inwardlyfrom the inner periphery 138 a of the sprocket body 132 a. As shown inFIGS. 7 and 8, the axially projecting portions 166 a of the sprocket Saaxially bulge towards the sprocket Sb on the first axial surface 152 aside, which define the axially recessed portions 168 a of the sprocketSa that are axially recessed towards the sprocket Sb on the second axialsurface 154 a side.

Similarly, in the illustrated embodiment, as shown in FIGS. 5 to 8, thefirst layered member 142 b of the sprocket Sb extends radially inwardlyfrom the inner periphery 138 b of the sprocket body 132 b. Specifically,the first layered member 142 b of the sprocket Sb has a sprocket supportmember 162 b. In the illustrated embodiment, the sprocket support member162 b has a plurality of (e.g., six in this embodiment) sprocket arms163 b radially connecting the inner periphery 138 b of the first layeredmember 142 b to a center boss 164 b. Of course, it will be apparent tothose skilled in the art from this disclosure that the number ofsprocket arms 163 b can be more than or less than six as needed and/ordesired. Specifically, in the illustrated embodiment, each of thesprocket arms 163 b extends in a direction slanted relative to theradial direction of the rotational axis X1. The center boss 164 b has abicycle hub engaging profile 165 b on an inner peripheral surface of thecenter boss 164 b. In other words, the first layered member 142 b hasthe bicycle hub engaging profile 165 b at a location of a radially innerend of the sprocket support member 162 b of the first layered member 142b. The bicycle hub engaging profile 165 b defines a plurality ofengaging splines that is dimensioned to be non-rotatably engage withsplines of the freewheel (not shown) of the rear bicycle hub 11 in arelatively conventional manner. Preferably, the bicycle hub engagingprofile 165 b is configured so that the rear sprocket assembly 112 canonly fit on the freewheel in a single orientation.

As shown in FIG. 5 to 8, each of the sprocket arms 163 b of the firstlayered member 142 b has an axially projecting portion 166 b and anaxially recessed portion 168 b. The axially projecting portions 166 band the axially recessed portions 168 b are positioned radially inwardlyfrom the inner periphery 138 b of the sprocket body 132 b. As shown inFIGS. 7 and 8, the axially projecting portions 166 b of the sprocket Saaxially bulge towards the sprocket Sb on the first axial surface 152 bside, which defines the axially recessed portions 168 b of the sprocketSa that are axially recessed towards the sprocket Sb on the second axialsurface 154 b side.

As shown in FIGS. 7 and 8, the axially projecting portions 166 a of thesprocket Sa (e.g., one of the bicycle sprockets) mates with the axiallyrecessed portion 168 b of the sprocket Sb (e.g., an adjacent one of thebicycle sprockets) adjacent to the sprocket Sa (e.g., one of the bicyclesprockets) while the sprockets Sa and Sb (e.g., bicycle sprockets) areattached to each other. Specifically, in the illustrated embodiment,while the sprockets Sa and Sb are attached to each other, the centerbosses 164 a and 164 b are concentrically aligned relative to eachother. In the illustrated embodiment, the center bosses 164 a and 164 bare identically formed relative to each other for receiving thefreewheel of the rear bicycle hub 11 therethrough. Furthermore, in theillustrated embodiment, an outer profile of each of the axiallyprojecting portions 166 a of the sprocket Sa is dimensioned to matchwith an inner profile of respective one of the axially recessed portions168 b of the sprocket Sb. Thus, the sprockets Sa and Sb are fittedly anddetachably coupled to each other. Furthermore, an axial height of theaxially projecting portion 166 a of the sprocket Sa and an axial depthof the axially recessed portion 168 b of the sprocket Sb are dimensionedsuch that the sprocket bodies 132 a and 132 b and the sprocket teeth 134a and 134 b of the sprockets Sa and Sb are axially spaced from eachother at a predetermined interval.

In the illustrated embodiment, the first layered member 142 a of thesprocket Sa is integrally formed as a one-piece, unitary member, whilethe first layered member 142 b of the sprocket Sb is integrally formedas a one-piece, unitary member. The first layered members 142 a and 142b of the sprockets Sa and Sb have the sprocket support members 162 a and162 b, respectively, which support the sprockets Sa and Sb on the rearbicycle hub 11. In other words, the sprocket support members 162 a and162 b form a sprocket support member to which the sprockets Sa and Sb(e.g., bicycle sprockets) are mounted. Thus, in the illustratedembodiment, the bicycle sprocket assembly 112 has the sprockets Sa andSb (e.g., a plurality of the bicycle sprockets), and the sprocketsupport members 162 a and 162 b (e.g., a sprocket support member) towhich the sprockets Sa and Sb are mounted.

In the illustrated embodiment, the sprockets Sa and Sb include the firstlayered members 142 a and 142 b, the second layered members 144 a and144 b, the third layered members 146 a and 146 b, and the coating layers148 a and 148 b, respectively. However, the multi-layered structure ofthe sprockets Sa and Sb are not limited to this. For example, thesprockets Sa and Sb can only include the first layered members 142 a and142 b, the second layered members 144 a and 144 b and the third layeredmembers 146 a and 146 b without the coating layers 148 a and 148 b,respectively. Furthermore, as illustrated in FIG. 9, the sprockets Saand Sb can only include the first layered members 142 a and 142 b, thesecond layered members 144 a and 144 b and the coating layers 148 a and148 b, without the third layered members 146 a and 146 b, respectively.Furthermore, the sprockets Sa and Sb can only include the first layeredmembers 142 a and 142 b, the third layered members 146 a and 146 b andthe coating layers 148 a and 148 b, without the second layered members144 a and 144 b, respectively.

More specifically, as shown in FIG. 9, the sprocket body 132 a and thesprocket teeth 134 a (e.g., at least one of the sprocket teeth or theplurality of sprocket teeth) of the sprocket Sa includes the firstlayered member 142 a and the second layered member 144 a. Furthermore,as shown in FIG. 9, the sprocket teeth 134 a further includes thecoating layer 148 a formed on the radially end surface 156 a of thefirst layered member 142 a. The first layered member 142 a has the firstaxial surface 152 a and the second axial surface 154 a opposite to thefirst axial surface 152 a. The second layered member 144 a has a thirdaxial surface 158 a and a fourth axial surface 160 a opposite to thethird axial surface 158 a. The third axial surface 158 a of the secondlayered member 144 a is attached to the first axial surface 152 a of thefirst layered member 142 a. In other words, the third axial surface 158a of the second layered member 144 a directly contacts with and isdirectly attached to the first axial surface 152 a of the first layeredmember 142 a. The first and second layered members 142 a and 144 aoverlap each other in the axial direction as viewed parallel to therotational axis X1. The first and second layered members 142 a and 144 ado not overlap each other in the radial direction as viewedperpendicularly to the rotational axis X1. The second axial surface 154a of the first layered member 142 a and the fourth axial surface 160 aof the second layered member 144 a are exposed. In other words, nolayers are axially formed on the second axial surface 154 a of the firstlayered member 142 a and the fourth axial surface 160 a of the secondlayered member 144 a. In the illustrated embodiment, the first layeredmember 142 a has a specific gravity that is less than that of the secondlayered member 144 a. Each of the first and second layered members 142 aand 144 a has an axial thickness more than or equal to 0.1 mm. Otherthan the multi-layered structure at the sprocket body 132 a and thesprocket teeth 134 a, the sprocket Sa shown in FIG. 9 is identical tothe sprocket Sa shown in FIGS. 4 to 8. Thus, the detailed configurationof the sprocket Sa will be omitted for the sake of brevity.

Similarly, as shown in FIG. 9, the sprocket body 132 b and the sprocketteeth 134 b (e.g., at least one of the sprocket teeth or the pluralityof sprocket teeth) of the sprocket Sa includes the first layered member142 b and the second layered member 144 b. Furthermore, as shown in FIG.9, the sprocket teeth 134 b further includes the coating layer 148 bformed on the radially end surface 156 b of the first layered member 142b. The first layered member 142 b has the first axial surface 152 b andthe second axial surface 154 b opposite to the first axial surface 152b. The second layered member 144 b has a third axial surface 158 b and afourth axial surface 160 b opposite to the third axial surface 158 b.The third axial surface 158 b of the second layered member 144 b isattached to the first axial surface 152 b of the first layered member142 b. In other words, the third axial surface 158 b of the secondlayered member 144 b directly contacts with and is directly attached tothe first axial surface 152 b of the first layered member 142 b. Thefirst and second layered members 142 b and 144 b overlap each other inthe axial direction as viewed parallel to the rotational axis X1. Thefirst and second layered members 142 b and 144 b do not overlap eachother in the radial direction as viewed perpendicularly to therotational axis X1. The second axial surface 154 b of the first layeredmember 142 b and the fourth axial surface 160 b of the second layeredmember 144 b are exposed. In other words, no layers are axially formedon the second axial surface 154 a of the first layered member 142 a andthe fourth axial surface 160 a of the second layered member 144 a. Inthe illustrated embodiment, the first layered member 142 b has aspecific gravity that is less than that of the second layered member 144b. Each of the first and second layered members 142 a and 144 a has anaxial thickness more than or equal to 0.1 mm. Other than themulti-layered structure at the sprocket body 132 b and the sprocketteeth 134 b, the sprocket Sb shown in FIG. 9 is identical to thesprocket Sb shown in FIGS. 4 to 8. Thus, the detailed configuration ofthe sprocket Sb will be omitted for the sake of brevity.

As shown in FIG. 9, the sprockets Sa and Sb includes the first layeredmembers 142 a and 142 b, the second layered members 144 a and 144 b, andthe coating layers 148 a and 148 b, respectively. However, themulti-layered structures of the sprockets Sa and Sb are not limited tothis. The sprockets Sa and Sb can only include the first layered members142 a and 142 b, the second layered members 144 a and 144 b without thecoating layers 148 a and 148 b, respectively.

In the illustrated embodiment, as shown in FIGS. 4 to 9, the sprocketbody 132 a and the sprocket teeth 134 a has the multi-layered structure.However, only the sprocket teeth 134 a can have the multi-layeredstructure as shown in FIGS. 4 to 9. Furthermore, in the illustratedembodiment, all of the sprocket teeth 134 a have the multi-layeredstructure as shown in FIGS. 4 to 9. However, only one(s) of the sprocketteeth 134 a can have the multi-layered structure as shown in FIGS. 4 to9. Similarly, in the illustrated embodiment, as shown in FIG. 4 to 9,the sprocket body 132 b and the sprocket teeth 134 b has themulti-layered structure. However, only the sprocket teeth 134 b can havethe multi-layered structure as shown in FIG. 4 to 9. Furthermore, in theillustrated embodiment, all of the sprocket teeth 134 b have themulti-layered structure as shown in FIG. 4 to 9. However, only one(s) ofthe sprocket teeth 134 b can have the multi-layered structure as shownin FIG. 4 to 9.

In the illustrated embodiment, as shown in FIGS. 4 to 8, the sprocketsSa and Sb are independently formed as separate members, and aredetachably coupled to each other. However, the sprockets Sa and Sb canalso be non-detachably coupled to each other. For example, as shown inFIGS. 10 and 11, the rear sprocket assembly 112 (e.g., a multiplesprocket assembly) includes the sprockets Sa and Sb (e.g., a pluralityof the bicycle sprockets) and a sprocket support member 162 c to whichthe sprockets Sa and Sb are mounted. In other words, in the illustratedembodiment, the sprockets Sa and Sb include the sprocket support member162 c as a common sprocket support member. The sprocket support member162 c has a unitary one-piece structure. In particular, in theillustrated embodiment, the sprocket support member 162 c is identicalto an integral combination of the sprocket support members 162 a and 162b as shown in FIG. 7. In other words, in the illustrated embodiment, thesprockets Sa and Sb have the first layered members 142 a and 142 b thatare integrally coupled to each other at the sprocket support member 162c. Furthermore, in the illustrated embodiment, the sprocket supportmember 162 c has a plurality of (six in this embodiment) sprocket arms163 c radially connecting the inner peripheries 138 a and 138 b of thefirst layered members 142 a and 142 b to a center boss 164 c.Specifically, in the illustrated embodiment, each of the sprocket arms163 c extends in a direction slanted relative to the radial direction ofthe rotational axis X1. The center boss 164 c has a bicycle hub engagingprofile 165 c on an inner peripheral surface of the center boss 164 c.In other words, the first layered members 142 a and 142 b have thebicycle hub engaging profile 165 c at a location of a radially inner endof the sprocket support member 162 c. The bicycle hub engaging profile165 c defines a plurality of engaging splines that is dimensioned to benon-rotatably engage with splines of the freewheel (not shown) of therear bicycle hub 11 (FIG. 1) in a relatively conventional manner.Preferably, the bicycle hub engaging profile 165 c is configured so thatthe rear sprocket assembly 112 can only fit on the freewheel in a singleorientation.

Furthermore, as shown in FIG. 11, each of the sprocket arms 163 c has anaxially projecting portion 166 c and an axially recessed portion 168 c.The axially projecting portions 166 c and the axially recessed portions168 c are positioned radially inwardly from the inner peripheries 138 aand 138 b of the sprocket bodies 132 a and 132 b. As shown in FIG. 11,the axially projecting portions 166 c axially bulge towards a firstaxial side, which define the axially recessed portions 168 c that areaxially recessed towards the first axial side. Of course, it will beapparent to those skilled in the art from this disclosure that each ofthe sprocket arms 163 c does not need to have the axially recessedportions 168 c when the sprocket Sa is the largest sprocket of the rearsprocket assembly 112.

In the illustrated embodiment, the sprocket S is the largest sprocket ofthe rear sprocket assembly 112. However, any one(s) of adjacent pairs ofthe sprockets S of the rear sprocket assembly 112 can include the sameconfiguration as the sprockets Sa and Sb. Moreover, any one(s) ofadjacent pairs of chain wheels or front sprockets of the front sprocketassembly 22 (FIG. 1) can also include the same configuration as thesprockets Sa and Sb.

Third Embodiment

Referring now to FIGS. 12 to 15, a front sprocket assembly 222 (e.g., amultiple sprocket assembly) in accordance with a third embodiment willnow be explained. The front sprocket assembly 222 is basically identicalto the front sprocket assembly 22 shown in FIG. 1, except that asprocket S of the front sprocket assembly 222 includes a multi-layeredstructure, as explained below.

In view of the similarity between the first and third embodiments, theparts of the third embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this third embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“200” added thereto. In any event, the descriptions of the parts of thethird embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis third embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure, as described below. The sprocket S is fixedly coupled to acrank arm (not shown) in a conventional manner. As shown in FIGS. 12 to15, the sprocket S basically includes a sprocket ring part 270, a bodypart 271 and a plurality of (e.g., four) attachment parts 272. Ofcourse, it will be apparent to those skilled in the art from thisdisclosure that the number of the attachment parts 272 can be more thanor less than four as needed and/or desired. The body part 271 isintegrally formed onto the sprocket ring part 270 and the attachmentparts 272 such that the sprocket ring part 270 and the attachment parts272 are at least partially embedded within the body part 271. In theillustrated embodiment, the sprocket ring part 270 is made of titaniumor stainless steel (SUS), while the body part 271 is made of syntheticresin. However, the sprocket ring part 270 can be made of the samematerial as the second layered member 44 or the third layered member 46of the sprocket S in accordance with the first embodiment, while thebody part 271 is made of the same material as the first layered member42 of the sprocket S in accordance with the first embodiment. Thus,detailed description of the material of the sprocket ring part 270 andthe body part 271 will be omitted for the sake of brevity.

In the illustrated embodiment, the body part 271 is molded onto thesprocket ring part 270 and the attachment parts 272 by, for example,insert molding or outsert molding. In this embodiment, the attachmentparts 272 are spaced radially inward of the sprocket ring part 270. Morespecifically, as shown in FIG. 12, the sprocket S (e.g., a bicyclesprocket) basically includes a sprocket body 232, and a plurality ofsprocket teeth 234. The sprocket body 232 has a rotational axis X1. Thesprocket body 232 includes an outer periphery 236 and an inner periphery238. The inner periphery 238 defines an opening 238 a for attaching thecrank arm thereto. The sprocket teeth 234 extend radially outwardly fromthe outer periphery 236 of the sprocket body 232. In the illustratedembodiment, the sprocket body 232 is defined as a part of the sprocket Sthat is radially inwardly disposed with respect to an imaginary circleconnecting innermost positions of gaps defined circumferentially betweenthe sprocket teeth 234. The sprocket S is the largest sprocket of thefront sprocket assembly 222. Thus, the total number of the sprocketteeth 234 is typically greater than the other sprockets of the frontsprocket assembly 222. In the illustrated embodiment, as shown in FIG.12, the total number of the sprocket teeth 234 is thirty-two. Of course,the total number of the sprocket teeth 234 can be different number asneeded and/or desired.

In the illustrated embodiment, as shown in FIG. 15, the sprocket ringpart 270 and the body part 271 form a multi-layered structure at thesprocket teeth 234 of the sprocket S. In particular, as shown in FIG.15, the sprocket teeth 234 including a first layered member 242 and asecond layered member 244. In the illustrated embodiment, the firstlayered member 242 is formed by the body part 271, while the secondlayered member 244 is formed by the sprocket ring part 270.Specifically, as shown in FIG. 15, the sprocket ring part 270 and thebody part 271 are arranged such that they form the multi-layeredstructure with the first and second layered members 242 and 244 at thesprocket teeth 234 of the sprocket, and such that the sprocket ring part270 is embedded within the body part 271 at the sprocket body 232 of thesprocket S. In the illustrated embodiment, the sprocket ring part 270radially inwardly extends with respect to the outer periphery 236 of thesprocket body 232. Thus, the sprocket body 232 of the sprocket Spartially includes the multi-layered structure with the first and secondlayered members 242 and 244. In other words, in the illustratedembodiment, the sprocket body 232 also includes the first layered member242 and the second layered member 244. The first layered member 242 hasa first axial surface 252 and a second axial surface 254 opposite to thefirst axial surface 252. The second layered member 244 has a third axialsurface 258 and a fourth axial surface 260 opposite to the third axialsurface 258. The third axial surface 258 of the second layered member244 is attached to the first axial surface 252 of the first layeredmember 242. In other words, the third axial surface 258 of the secondlayered member 244 directly contacts with and is directly attached tothe first axial surface 252 of the first layered member 242. The firstand second layered members 242 and 244 are attached with respect to eachother in the same fixing manner as discussed in the first embodiment.The first and second layered members 242 and 244 overlap each other inthe axial direction as viewed parallel to the rotational axis X1 at thesprocket teeth 234 of the sprocket S. The first and second layeredmembers 242 and 244 do not overlap each other in the radial direction asviewed perpendicularly to the rotational axis X1 at the sprocket teeth234 of the sprocket S. The second axial surface 254 of the first layeredmember 242 and the fourth axial surface 260 of the second layered member244 are exposed. In other words, no layers are axially formed on thesecond axial surface 254 of the first layered member 242 and the fourthaxial surface 260 of the second layered member 244. In the illustratedembodiment, the first layered member 242 has a specific gravity that isless than that of the second layered member 244. Each of the first andsecond layered members 242 and 244 has an axial thickness more than orequal to 0.1 mm.

As shown in FIGS. 14 and 15, the sprocket ring part 270 has a pluralityof through-holes 274 at the sprocket body 232 of the sprocket S. Thethrough-holes 274 of the sprocket ring part 270 extend between the thirdand fourth axial surfaces 258 and 260. As shown in FIG. 15, the bodypart 271 extends through the through-holes 274 of the sprocket ring part270. The through-holes 274 are formed preferably at equally spaced apartintervals in the circumferential direction of the sprocket ring part270. These through-holes 274 act as anchor structures for facilitatingthe non-rotatable connection of the body part 271 to the sprocket ringpart 270.

The attachment parts 272 are each formed as a separate member from thebody part 271 and the sprocket ring part 270. The attachment parts 272are at least partially embedded within the synthetic resin body part271. In this embodiment, the attachment parts 272 are almost completelyembedded within the body part 271. The attachment parts 272 arepreferably one-piece, unitary members that are formed of a hard rigidmaterial that is more rigid and/or harder than the synthetic resin bodypart 271. More preferably, the attachment parts 272 are formed of amaterial that is the same as the sprocket ring part 270.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure with the first layered member 242 and the second layeredmember 244 at the sprocket teeth 234. However, the multi-layeredstructure of the sprocket S is not limited to this. For example, thesprocket teeth 234 can further include a coating layer. The coatinglayer of the sprocket teeth 234 can include an identical configurationto the coating layer 48 as shown in FIG. 3 or the coating layers 148 aand 148 b as shown in FIG. 9. Thus, detailed description of the coatinglayer will be omitted for the sake of brevity. The coating layer can beformed on a radially end surface of the first layered member 242.

Fourth Embodiment

Referring now to FIGS. 16 to 18A, a rear sprocket assembly 312 (e.g., amultiple sprocket assembly) in accordance with a fourth embodiment willnow be explained. The rear sprocket assembly 312 is basically identicalto the rear sprocket assembly 12 in accordance with the firstembodiment, except for a configuration of a sprocket body 332, asexplained below.

In view of the similarity between the first and fourth embodiments, theparts of the fourth embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this fourth embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“300” added thereto. In any event, the descriptions of the parts of thefourth embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis fourth embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, a plurality of sprockets (e.g., aplurality of bicycle sprockets) of the rear sprocket assembly 312includes a sprocket S with a multi-layered structure, as describedbelow. Specifically, in the illustrated embodiment, as shown in FIG. 16,the sprocket S is the largest sprocket of the rear sprocket assembly312. Of course, any one of the sprockets of the rear sprocket assembly312 can have this multi-layered structure. For example, in theillustrated embodiment, an adjacent sprocket S′ (e.g., an adjacent oneof the bicycle sprockets) (FIG. 18B) adjacent to the sprocket S can alsohave this multi-layered structure. In the illustrated embodiment, sincethe sprocket S is the largest sprocket, the adjacent sprocket S′ is thesecond largest sprocket of the rear sprocket assembly 312. On the otherhand, in the illustrated embodiment, the other sprockets other than thesprockets S and S′ can have any conventional configuration as neededand/or desired. For example, these sprockets other than the sprockets Sand S′ can be each formed as a one-piece, unitary member from a metallicmaterial that is suitable for a bicycle sprocket such as an iron or aniron alloy. Furthermore, the configuration of the sprockets S and S′ arebasically identical to each other except for the dimensions of thesprockets S and S′ and the number of sprocket teeth. Therefore, in theillustrated embodiment, the following disclosure will basically focus onthe configuration of the sprocket S for the sake of brevity, anddetailed description of the adjacent sprocket S′ will be omitted for thesake of brevity.

As shown in FIGS. 16 and 17, the sprocket S (e.g., a bicycle sprocket)basically includes a sprocket body 332, and a plurality of sprocketteeth 334. The sprocket body 332 has a rotational axis X1. The sprocketbody 332 includes an outer periphery 336 and an inner periphery 338. Thesprocket teeth 334 extend radially outwardly from the outer periphery336 of the sprocket body 332. In the illustrated embodiment, thesprocket S is the largest sprocket of the rear sprocket assembly 312. Asshown in FIGS. 16 and 17, the total number of the sprocket teeth 334 isthirty-six. Of course, the total number of the sprocket teeth can bedifferent number as needed and/or desired.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure. Specifically, as shown in FIGS. 16 to 18A, the sprocket Sincludes a first layered member 342, a second layered member 344, athird layered member 346, and a coating layer 348. In the illustratedembodiment, the first, second and third layered members 342, 344 and 346radially outwardly extends from the inner periphery 338 of the sprocketbody 332 to the sprocket teeth 334. The multi-layered structure of thesprocket S is basically identical to that of the sprocket S inaccordance with the first embodiment, except that the sprocket body 332has a plurality of (e.g., six) axially projecting portions 366 and aplurality of (e.g., six) axially recessed portions 368. Of course, itwill be apparent to those skilled in the art from this disclosure thatthe number of the axially projecting portions 366 can be more than orless than six as needed and/or desired, and that the number of theaxially recessed portions 368 can be more than or less than six asneeded and/or desired. The axially projecting portions 366 and theaxially recessed portion 368 are positioned at the sprocket body 332. Inother words, the multi-layered structure of the sprocket teeth 334 ofthe sprocket S is identical to that of the sprocket S in accordance withthe first embodiment. Specifically, the configurations of the first,second and third layered members 342, 344 and 346 and the coating layer348 at the sprocket teeth 334 of the sprocket S are identical to thoseof the first, second and third layered members 42, 44 and 46 and thecoating layer 48 at the sprocket teeth 34 of the sprocket S inaccordance with the first embodiment. Furthermore, the materials of thefirst, second and third layered members 342, 344 and 346 and the coatinglayer 348 of the sprocket S are the same as those of the first, secondand third layered members 42, 44 and 46 and the coating layer 48 of thesprocket S in accordance with the first embodiment, respectively. Forexample, the first layered member 342 has a specific gravity that isless than those of the second layered member 344 and the third layeredmember 346. Thus, the detailed description of the multi-layeredstructure of the sprocket S will be omitted for the sake of brevity. Itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the parts of sprocket S inaccordance with the first embodiment also apply to the parts of thesprocket S having the same name, except as discussed and/or illustratedherein.

As illustrated in FIG. 18A, the first layered member 342 has a firstaxial surface 352 and a second axial surface 354 opposite to the firstaxial surface 352. The second layered member 344 is attached to thefirst axial surface 352 of the first layered member 342. The thirdlayered member 346 is attached to the second axial surface 354 of thefirst layered member 342. The coating layer 348 is formed on a radiallyend surface 356 of the first layered member 42. The first, second andthird layered members 342, 344 and 346 and the coating layer 348 areattached with respect to each other in the same fixing manner asdiscussed in the first embodiment. Thus, the detailed description willbe omitted for the sake of brevity.

In the illustrated embodiment, the first layered member 342 has aplurality of table portions 378. The table portions 378 arecircumferentially spaced from each other at predetermined interval aboutthe inner periphery 338 of the sprocket body 332. The axially projectingportions 366 and the axially recessed portions 368 are formed on thetable portions 378, respectively. Specifically, each of the axiallyprojecting portions 366 has a plurality of (e.g., three) projections 366a that is formed on one axial side of respective one of the tableportions 378, while each of the axially recessed portions 368 has aplurality of (e.g., three) recesses 368 a that is formed on the otheraxial side of the respective one of the table portions 378. Inparticular, as shown in FIG. 18A, each of the axially projectingportions 366 bulges towards the first axial surface 352 side at therespective one of the table portions 378, which defines the axiallyrecessed portions 368 on the second axial surface 354 side at therespective one of the table portions 378. In the illustrated embodiment,the first layered member 342 is integrally formed as a one-piece,unitary member. Of course, it will be apparent to those skilled in theart from this disclosure that the number of the projections 366 a ofeach of the axially projecting portions 366 can be more than or lessthan three as needed and/or desired, and that the number of the recesses368 a of each of the axially recessed portions 368 can be more than orless than three as needed and/or desired.

As shown in FIG. 18A, the first and second layered members 342 and 344overlap each other in an axial direction as viewed parallel to therotational axis X1. Specifically, the first and second layered members342 and 344 overlap each other in the axial direction at an area exceptfor the table portions 378. As shown in FIG. 18A, the table portions 378are integrally formed with the first layered member 342 as a one-piece,unitary member. Thus, as shown in FIG. 16, the first layered member 342is axially exposed at the table portions 378 through notches 382 of thesecond layered member 344 in the axial direction as viewed parallel tothe rotational axis X1. Furthermore, as shown in FIG. 18A, the first andsecond layered members 342 and 344 do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis X1 at leastat the sprocket teeth 334 of the sprocket S. On the other hand, thefirst and third layered members 342 and 346 overlap each other in theaxial direction as viewed parallel to the rotational axis X1.Specifically, the first and third layered members 342 and 346 overlapeach other in the axial direction at an area except for the tableportions 378. Furthermore, the first and third layered members 342 and346 do not overlap each other in the radial direction as viewedperpendicularly to the rotational axis X1 at least at the sprocket teeth334 of the sprocket S. As shown in FIG. 18A, the first layered member342 is also axially exposed at the table portions 378 through notches384 of the third layered member 346 in the axial direction as viewedparallel to the rotational axis X1. Thus, in the illustrated embodiment,the sprocket body 332 partially includes the first layered member 342,the second layered member 344 and the third layered member 346 at thearea except for the table portions 378. In other words, as shown in FIG.18A, the sprocket body 332 only includes the first layered member 342 atthe table portions 378. In the illustrated embodiment, the axialdimension or thickness T1 of the first layered member 342 at the tableportions 378 is larger than the axial dimension or thickness T2 of thesprocket teeth 334. Thus, as shown in FIG. 18A, the table portions 378of the first layered member 342 radially contact with inner surfaces ofthe notches 382 of the second layered member 344 and inner surfaces ofthe notches 384 of the third layered member 346. Furthermore, in theillustrated embodiment, the second and third layered members 344 and 346have an identical shape.

As shown in FIG. 18B, the rear sprocket assembly 312 includes thesprocket S and the adjacent sprocket S′ (e.g., a plurality of bicyclesprockets). The sprocket S and the adjacent sprocket S′ are detachablycoupled to each other. Specifically, as shown in FIG. 18B, similar tothe sprocket S, the adjacent sprocket S′ has a plurality of axiallyprojecting portions 366′ and a plurality of axially recessed portions368′. The axially projecting portions 366 of the sprocket S (e.g., oneof the bicycle sprockets) mates with axially recessed portions 368 ofthe adjacent sprocket S′ (e.g., an adjacent one of the bicyclesprockets) adjacent to the sprocket S (e.g., one of the bicyclesprockets) while the sprockets S and S′ (e.g., bicycle sprockets) areattached to each other. Specifically, in the illustrated embodiment, anouter profile of each of the axially projecting portions 366 of thesprocket S is dimensioned to match with an inner profile of respectiveone of the axially recessed portions 368′ of the adjacent sprocket S′.Thus, the sprockets S and S′ are fittedly and detachably coupled to eachother. Furthermore, an axial height of the axially projecting portion366 of the sprocket S and an axial depth of the axially recessed portion368′ of the adjacent sprocket S′ are dimensioned such that the sprocketbodies 332 and 332′ and the sprocket teeth 334 and 334′ of the sprocketsS and S′ are axially spaced from each other at a predetermined interval.

In the illustrated embodiment, the sprocket S includes the first layeredmember 342, the second layered member 344, the third layered member 346,and the coating layer 348. However, the multi-layered structure of thesprocket S is not limited to this. The sprocket S can only include thefirst layered member 342, the second layered member 344 and the thirdlayered member 346 without the coating layer 348. Furthermore, thesprocket S can only include the first layered member 342, the secondlayered member 344 and the coating layer 348 without the third layeredmember 346. In this case, a third axial surface of the second layeredmember 344 is attached to the first axial surface 352 of the firstlayered member 342. However, the second axial surface 354 of the firstlayered member 342 and a fourth axial surface of the second layeredmember 344 that is opposite the third axial surface are exposed.Furthermore, the sprocket S can only include the first layered member342, the third layered member 346 and the coating layer 348 without thesecond layered member 344. In this case, the first axial surface 352 ofthe first layered member 342 is axially exposed.

Fifth Embodiment

Referring now to FIGS. 19 to 21, a rear sprocket assembly 412 (e.g., amultiple sprocket assembly) in accordance with a fifth embodiment willnow be explained. The rear sprocket assembly 412 is basically identicalto the rear sprocket assembly 12 in accordance with the firstembodiment, except for a configuration of a sprocket body 432, asexplained below.

In view of the similarity between the first and fifth embodiments, theparts of the fifth embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this fifth embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“400” added thereto. In any event, the descriptions of the parts of thefifth embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis fifth embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, a plurality of sprockets (e.g., aplurality of bicycle sprockets) of the rear sprocket assembly 412includes a sprocket S with a multi-layered structure, as describedbelow. Specifically, in the illustrated embodiment, as shown in FIG. 19,the sprocket S is the largest sprocket of the rear sprocket assembly412. Of course, any one of the sprockets of the rear sprocket assembly412 can have this multi-layered structure. For example, in theillustrated embodiment, an adjacent sprocket (e.g., an adjacent one ofthe bicycle sprockets) adjacent to the sprocket S can also have thismulti-layered structure. In the illustrated embodiment, since thesprocket S is the largest sprocket, the adjacent sprocket is the secondlargest sprocket of the rear sprocket assembly 412. On the other hand,in the illustrated embodiment, the other sprockets other than thesprocket S and the adjacent sprocket can have any conventionalconfiguration as needed and/or desired. For example, these sprocketsother than the sprocket S and the adjacent sprocket can be each formedas a one-piece, unitary member from a metallic material that is suitablefor a bicycle sprocket such as an iron or an iron alloy. Furthermore,the configuration of the sprocket S and the adjacent sprocket arebasically identical to each other except for the dimensions and thenumber of sprocket teeth. Therefore, in the illustrated embodiment, thefollowing disclosure will basically focus on the configuration of thesprocket S for the sake of brevity, and detailed description of theadjacent sprocket will be omitted for the sake of brevity.

As shown in FIGS. 19 and 20, the sprocket S (e.g., a bicycle sprocket)basically includes a sprocket body 432, and a plurality of sprocketteeth 434. The sprocket body 432 has a rotational axis X1. The sprocketbody 432 includes an outer periphery 436 and an inner periphery 438. Thesprocket teeth 434 extend radially outwardly from the outer periphery436 of the sprocket body 432. In the illustrated embodiment, thesprocket S is the largest sprocket of the rear sprocket assembly 412. Asshown in FIGS. 19 and 20, the total number of the sprocket teeth 434 isthirty-six. Of course, the total number of the sprocket teeth can bedifferent number as needed and/or desired.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure. Specifically, as shown in FIGS. 19 to 21, the sprocket Sincludes a first layered member 442, a second layered member 444, athird layered member 446, and a coating layer 448. In the illustratedembodiment, the first, second and third layered members 442, 444 and 446radially outwardly extends from the inner periphery 438 of the sprocketbody 432 to the sprocket teeth 434. The multi-layered structure of thesprocket S is basically identical to that of the sprocket S inaccordance with the first embodiment, except that the sprocket body 432has a plurality of (e.g., six) axially projecting portions 466 and aplurality of (e.g., six) axially recessed portions 468. Of course, itwill be apparent to those skilled in the art from this disclosure thatthe number of the axially projecting portions 466 can be more than orless than six as needed and/or desired, and that the number of theaxially recessed portions 468 can be more than or less than six asneeded and/or desired. The axially projecting portions 466 and theaxially recessed portion 468 are positioned at the sprocket body 432. Inother words, the multi-layered structure of the sprocket teeth 434 ofthe sprocket S is identical to that of the sprocket S in accordance withthe first embodiment. Specifically, the configurations of the first,second and third layered members 442, 444 and 446 and the coating layer448 at the sprocket teeth 434 of the sprocket S are identical to thoseof the first, second and third layered members 42, 44 and 46 and thecoating layer 48 at the sprocket teeth 34 of the sprocket S inaccordance with the first embodiment. Furthermore, the materials of thefirst, second and third layered members 442, 444 and 446 and the coatinglayer 448 of the sprocket S are same as those of the first, second andthird layered members 42, 44 and 46 and the coating layer 48 of thesprocket S in accordance with the first embodiment, respectively. Forexample, the first layered member 442 has a specific gravity that isless than those of the second layered member 444 and the third layeredmember 446. Thus, the detailed description of the multi-layeredstructure of the sprocket S will be omitted for the sake of brevity. Itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the parts of sprocket S inaccordance with the first embodiment also apply to the parts of thesprocket S having the same name, except as discussed and/or illustratedherein.

As illustrated in FIG. 21, the first layered member 442 has a firstaxial surface 452 and a second axial surface 454 opposite to the firstaxial surface 452. The second layered member 444 is attached to thefirst axial surface 452 of the first layered member 442. The thirdlayered member 446 is attached to the second axial surface 454 of thefirst layered member 442. The coating layer 448 is formed on a radiallyend surface 456 of the first layered member 442. The first, second andthird layered members 442, 444 and 446 and the coating layer 448 areattached with respect to each other in the same fixing manner asdiscussed in the first embodiment. Thus, the detailed description willbe omitted for the sake of brevity.

In the illustrated embodiment, the first layered member 442 has aplurality of table portions 478. The table portions 478 arecircumferentially spaced from each other at predetermined interval aboutthe inner periphery 438 of the sprocket body 432. The axially projectingportions 466 and the axially recessed portions 468 are formed on thetable portions 478, respectively. Specifically, each of the axiallyprojecting portions 466 has a plurality of (e.g., three) projections 466a that is formed on one axial side of respective one of the tableportions 478, while each of the axially recessed portions 468 has aplurality of (e.g., three) recesses 468 a that is formed on the otheraxial side of the respective one of the table portions 478. Inparticular, as shown in FIG. 21, each of the axially projecting portions466 bulges towards the first axial surface 452 side at the respectiveone of the table portions 478, which defines the axially recessedportions 468 on the second axial surface 454 side at the respective oneof the table portions 478. In the illustrated embodiment, the firstlayered member 442 is integrally formed as a one-piece, unitary member.Of course, it will be apparent to those skilled in the art from thisdisclosure that the number of the projections 466 a of each of theaxially projecting portions 466 can be more than or less than three asneeded and/or desired, and that the number of the recesses 468 a of eachof the axially recessed portions 468 can be more than or less than threeas needed and/or desired.

As shown in FIG. 21, the first and second layered members 442 and 444overlap each other in an axial direction as viewed parallel to therotational axis X1. Specifically, the first and second layered members442 and 444 overlap each other in the axial direction at an area exceptfor the table portions 478. As shown in FIG. 21, the table portions 478are integrally formed with the first layered member 442 as a one-piece,unitary member. Thus, as shown in FIG. 19, the first layered member 442is axially exposed at the table portions 478 through notches 482 of thesecond layered member 444 in the axial direction as viewed parallel tothe rotational axis X1. Furthermore, as shown in FIG. 21, the first andsecond layered members 442 and 444 do not overlap each other in a radialdirection as viewed perpendicularly to the rotational axis X1 at leastat the sprocket teeth 434 of the sprocket S. On the other hand, thefirst and third layered members 442 and 446 overlap each other in theaxial direction as viewed parallel to the rotational axis X1.Specifically, the first and third layered members 442 and 446 overlapeach other in the axial direction at an area except for the tableportions 478. Furthermore, the first and third layered members 442 and446 do not overlap each other in the radial direction as viewedperpendicularly to the rotational axis X1 at least at the sprocket teeth434 of the sprocket S. As shown in FIG. 21, the first layered member 442is also axially exposed at the table portions 478 through notches 484 ofthe third layered member 446 in the axial direction as viewed parallelto the rotational axis X1. Thus, in the illustrated embodiment, thesprocket body 432 partially includes the first layered member 442, thesecond layered member 444 and the third layered member 446 at the areaexcept for the table portions 478. In other words, as shown in FIG. 21,the sprocket body 432 only includes the first layered member 442 at thetable portions 478. In the illustrated embodiment, the axial dimensionor thickness T3 of the first layered member 442 at the table portions478 is smaller than the axial dimension or thickness T4 of the sprocketteeth 434. Thus, as shown in FIG. 21, the table portions 478 of thefirst layered member 442 is axially recessed relative to the secondlayered member 444 and relative to the third layered member 446.Specifically, the table portions 478 have the same axial dimension T3 asthe axial dimension or thickness of the first layered member 442 at thesprocket teeth 434. Furthermore, in the illustrated embodiment, thesecond and third layered members 444 and 446 have an identical shape.

As mentioned above, the rear sprocket assembly 412 includes the sprocketS and the adjacent sprocket (e.g., a plurality of bicycle sprockets).The sprocket S and the adjacent sprocket are detachably coupled to eachother. Specifically, similar to the rear sprocket assembly 312 shown inFIG. 18B, the axially projecting portions 466 of the sprocket S (e.g.,one of the bicycle sprockets) mates with axially recessed portions ofthe adjacent sprocket (e.g., an adjacent one of the bicycle sprockets)adjacent to the sprocket S (e.g., one of the bicycle sprockets) whilethe sprocket S and the adjacent sprocket (e.g., bicycle sprockets) areattached to each other. Specifically, in the illustrated embodiment, anouter profile of each of the axially projecting portions 466 of thesprocket S is dimensioned to match with an inner profile of respectiveone of the axially recessed portion of the adjacent sprocket. Thus, thesprocket S and the adjacent sprocket are fittedly and detachably coupledto each other. Furthermore, an axial height of the axially projectingportions 466 of the sprocket S and an axial depth of the axiallyrecessed portions of the adjacent sprocket are dimensioned such that thesprocket S and the adjacent sprocket are axially spaced from each otherat a predetermined interval.

In the illustrated embodiment, the sprocket S includes the first layeredmember 442, the second layered member 444, the third layered member 446,and the coating layer 448. However, the multi-layered structure of thesprocket S is not limited to this. The sprocket S can only include thefirst layered member 442, the second layered member 444 and the thirdlayered member 446 without the coating layer 448. Furthermore, thesprocket S can only include the first layered member 442, the secondlayered member 444 and the coating layer 448 without the third layeredmember 446. In this case, a third axial surface of the second layeredmember 444 is attached to the first axial surface 452 of the firstlayered member 442. However, the second axial surface 454 of the firstlayered member 442 and a fourth axial surface of the second layeredmember 444 that is opposite the third axial surface are exposed.Furthermore, alternatively, the sprocket S can only include the firstlayered member 442, the third layered member 446 and the coating layer448 without the second layered member 444. In this case, the first axialsurface 452 of the first layered member 442 is axially exposed.

Sixth Embodiment

Referring now to FIGS. 22 and 23, a rear sprocket assembly 512 (e.g., amultiple sprocket assembly) in accordance with a sixth embodiment willnow be explained. The rear sprocket assembly 512 is basically identicalto the rear sprocket assembly 12 in accordance with the firstembodiment, except for a configuration of a sprocket body 532, asexplained below.

In view of the similarity between the first and sixth embodiments, theparts of the sixth embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this sixth embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“500” added thereto. In any event, the descriptions of the parts of thesixth embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis sixth embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, a plurality of sprockets (e.g., aplurality of bicycle sprockets) of the rear sprocket assembly 512includes a sprocket S with a multi-layered structure, as describedbelow. Specifically, in the illustrated embodiment, as shown in FIG. 22,the sprocket S is the largest sprocket of the rear sprocket assembly512. Of course, any one of the sprockets of the rear sprocket assembly512 can have this multi-layered structure. For example, in theillustrated embodiment, an adjacent sprocket (e.g., an adjacent one ofthe bicycle sprockets) adjacent to the sprocket S can also have thismulti-layered structure. In the illustrated embodiment, since thesprocket S is the largest sprocket, the adjacent sprocket is the secondlargest sprocket of the rear sprocket assembly 512. On the other hand,in the illustrated embodiment, the other sprockets other than thesprocket S and the adjacent sprocket can have any conventionalconfiguration as needed and/or desired. For example, these sprocketsother than the sprocket S and the adjacent sprocket can be each formedas a one-piece, unitary member from a metallic material that is suitablefor a bicycle sprocket such as an iron or an iron alloy. Furthermore,the configuration of the sprocket S and the adjacent sprocket arebasically identical to each other except for the dimensions and thenumber of sprocket teeth. Therefore, in the illustrated embodiment, thefollowing disclosure will basically focus on the configuration of thesprocket S for the sake of brevity, and detailed description of theadjacent sprocket will be omitted for the sake of brevity.

As shown in FIGS. 22 and 23, the sprocket S (e.g., a bicycle sprocket)basically includes a sprocket body 532, and a plurality of sprocketteeth 534. The sprocket body 532 has a rotational axis X1. The sprocketbody 532 includes an outer periphery 536 and an inner periphery 538. Thesprocket teeth 534 extend radially outwardly from the outer periphery536 of the sprocket body 532. In the illustrated embodiment, thesprocket S is the largest sprocket of the rear sprocket assembly 512. Asshown in FIGS. 22 and 23, the total number of the sprocket teeth 534 isthirty-six. Of course, the total number of the sprocket teeth can bedifferent number as needed and/or desired.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure. Specifically, as shown in FIGS. 22 and 23, the sprocket Sincludes a first layered member 542, a second layered member 544, athird layered member 546, and a coating layer 548. In the illustratedembodiment, the first, second and third layered members 542, 544 and 546radially outwardly extends from the inner periphery 538 of the sprocketbody 532 to the sprocket teeth 534. The multi-layered structure of thesprocket S is basically identical to that of the sprocket S inaccordance with the first embodiment, except that the sprocket body 532has a plurality of (e.g., six) axially projecting portions 566 and aplurality of (e.g., six) axially recessed portions 568. Of course, itwill be apparent to those skilled in the art from this disclosure thatthe number of the axially projecting portions 566 can be more than orless than six as needed and/or desired, and that the number of theaxially recessed portions 568 can be more than or less than six asneeded and/or desired. The axially projecting portions 566 and theaxially recessed portions 568 are positioned at the sprocket body 532.In other words, the multi-layered structure of the sprocket teeth 534 ofthe sprocket S is identical to that of the sprocket S in accordance withthe first embodiment. Specifically, the configurations of the first,second and third layered members 542, 544 and 546 and the coating layer548 at the sprocket teeth 534 of the sprocket S are identical to thoseof the first, second and third layered members 42, 44 and 46 and thecoating layer 48 at the sprocket teeth 34 of the sprocket S inaccordance with the first embodiment. Furthermore, the materials of thefirst, second and third layered members 542, 544 and 546 and the coatinglayer 548 of the sprocket S are same as those of the first, second andthird layered members 42, 44 and 46 and the coating layer 48 of thesprocket S in accordance with the first embodiment, respectively. Forexample, the first layered member 542 has a specific gravity that isless than those of the second layered member 544 and the third layeredmember 546. Thus, the detailed description of the multi-layeredstructure of the sprocket S will be omitted for the sake of brevity. Itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the parts of sprocket S inaccordance with the first embodiment also apply to the parts of thesprocket S having the same name, except as discussed and/or illustratedherein.

In the illustrated embodiment, the first layered member 542 has a firstaxial surface and a second axial surface opposite to the first axialsurface. The second layered member 544 is attached to the first axialsurface of the first layered member 542. The third layered member 546 isattached to the second axial surface of the first layered member 542.The coating layer 548 is formed on a radially end surface of the firstlayered member 542. The first, second and third layered members 542, 544and 546 and the coating layer 548 are attached with respect to eachother in the same fixing manner as discussed in the first embodiment.Thus, the detailed description will be omitted for the sake of brevity.

In the illustrated embodiment, the first layered member 542 has aplurality of (e.g., six) table portions 578. The table portions 578 arecircumferentially spaced from each other at predetermined interval aboutthe inner periphery 538 of the sprocket body 532. The axially projectingportions 566 and the axially recessed portions 568 are formed on thetable portions 578, respectively. Specifically, each of the axiallyprojecting portions 566 has a single projection 566 a that is formed onone axial side of respective one of the table portions 578, while eachof the axially recessed portions 568 has a single recess 568 a that isformed on the other axial side of the respective one of the tableportions 578. In particular, in the illustrated embodiment, each of theaxially projecting portions 566 bulges towards the first axial surfaceside at the respective one of the table portions 578, which defines theaxially recessed portions 568 on the second axial surface side at therespective one of the table portions 578. In the illustrated embodiment,the first layered member 542 is integrally formed as a one-piece,unitary member.

As shown in FIG. 22, the first and second layered members 542 and 544overlap each other in an axial direction as viewed parallel to therotational axis X1. Specifically, the first and second layered members542 and 544 overlap each other in the axial direction at an area exceptfor the table portions 578. As shown in FIG. 22, the table portions 578are integrally formed with the first layered member 542 as a one-piece,unitary member. Thus, as shown in FIG. 22, the first layered member 542is axially exposed at the table portions 578 through notches 582 of thesecond layered member 544 in the axial direction as viewed parallel tothe rotational axis X1. Furthermore, in the illustrated embodiment, thefirst and second layered members 542 and 544 do not overlap each otherin a radial direction as viewed perpendicularly to the rotational axisX1 at least at the sprocket teeth 534 of the sprocket S. On the otherhand, as shown in FIG. 23, the first and third layered members 542 and546 overlap each other in the axial direction as viewed parallel to therotational axis X1. Specifically, the first and third layered members542 and 546 overlap each other in the axial direction at an area exceptfor the table portions 578. Furthermore, the first and third layeredmembers 542 and 546 do not overlap each other in the radial direction asviewed perpendicularly to the rotational axis X at least at the sprocketteeth 534 of the sprocket S. As shown in FIG. 23, the first layeredmember 542 is also axially exposed at the table portions 578 throughnotches 584 of the third layered member 546 in the axial direction asviewed parallel to the rotational axis X1. Thus, in the illustratedembodiment, the sprocket body 532 partially includes the first layeredmember 542, the second layered member 544 and the third layered member546 at the area except for the table portions 578. In other words, asshown in FIGS. 22 and 23, the sprocket body 532 only includes the firstlayered member 542 at the table portions 578. In the illustratedembodiment, the axial dimension or thickness of the first layered member542 at the table portions 578 is smaller than the axial dimension orthickness of the sprocket teeth 534. Thus, as shown in FIGS. 22 and 23,the table portions 578 of the first layered member 542 is axiallyrecessed relative to the second layered member 544 and relative to thethird layered member 546. Specifically, the table portions 578 have thesame axial dimension as the axial dimension or thickness of the firstlayered member 542 at the sprocket teeth 534. Furthermore, in theillustrated embodiment, the second and third layered members 544 and 546have an identical shape.

As mentioned above, the rear sprocket assembly 512 includes the sprocketS and the adjacent sprocket (e.g., a plurality of bicycle sprockets).The sprocket S and the adjacent sprocket are detachably coupled to eachother. Specifically, similar to the rear sprocket assembly 312 shown inFIG. 18B, the axially projecting portions 566 of the sprocket S (e.g.,one of the bicycle sprockets) mates with axially recessed portions ofthe adjacent sprocket (e.g., an adjacent one of the bicycle sprockets)adjacent to the sprocket S (e.g., one of the bicycle sprockets) whilethe sprocket S and the adjacent sprocket (e.g., bicycle sprockets) areattached to each other. Specifically, in the illustrated embodiment, anouter profile of each of the axially projecting portions 566 of thesprocket S is dimensioned to match with an inner profile of respectiveone of the axially recessed portion of the adjacent sprocket. Thus, thesprocket S and the adjacent sprocket are fittedly and detachably coupledto each other. Furthermore, an axial height of the axially projectingportions 566 of the sprocket S and an axial depth of the axiallyrecessed portions of the adjacent sprocket are dimensioned such that thesprocket S and the adjacent sprocket are axially spaced from each otherat a predetermined interval.

In the illustrated embodiment, the sprocket S includes the first layeredmember 542, the second layered member 544, the third layered member 546,and the coating layer 548. However, the multi-layered structure of thesprocket S is not limited to this. The sprocket S can only include thefirst layered member 542, the second layered member 544 and the thirdlayered member 546 without the coating layer 548. Furthermore, thesprocket S can only include the first layered member 542, the secondlayered member 544 and the coating layer 548 without the third layeredmember 546. In this case, a third axial surface of the second layeredmember 544 is attached to the first axial surface of the first layeredmember 542. However, the second axial surface of the first layeredmember 542 and a fourth axial surface of the second layered member 544that is opposite the third axial surface are exposed. Furthermore,alternatively, the sprocket S can only include the first layered member542, the third layered member 546 and the coating layer 548 without thesecond layered member 544. In this case, the first axial surface of thefirst layered member 542 is axially exposed.

Seventh Embodiment

Referring now to FIGS. 24 to 26, a rear sprocket assembly 612 (e.g., amultiple sprocket assembly) in accordance with a sixth embodiment willnow be explained. The rear sprocket assembly 612 is basically identicalto the rear sprocket assembly 12 in accordance with the firstembodiment, except for a configuration of a sprocket body 632, asexplained below.

In view of the similarity between the first and seventh embodiments, theparts of the seventh embodiment that are identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Also, parts of this seventh embodiment that arefunctionally identical and/or substantially identical to parts of thefirst embodiment will be given the same reference numerals but with“600” added thereto. In any event, the descriptions of the parts of theseventh embodiment that are substantially identical to the parts of thefirst embodiment may be omitted for the sake of brevity. However, itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the first embodiment also apply tothis seventh embodiment, except as discussed and/or illustrated herein.

In the illustrated embodiment, a plurality of sprockets (e.g., aplurality of bicycle sprockets) of the rear sprocket assembly 612includes a sprocket S with a multi-layered structure, as describedbelow. Specifically, in the illustrated embodiment, as shown in FIG. 24,the sprocket S is the largest sprocket of the rear sprocket assembly612. Of course, any one of the sprockets of the rear sprocket assembly612 can have this multi-layered structure. For example, in theillustrated embodiment, an adjacent sprocket (e.g., an adjacent one ofthe bicycle sprockets) adjacent to the sprocket S can also have thismulti-layered structure. In the illustrated embodiment, since thesprocket S is the largest sprocket, the adjacent sprocket is the secondlargest sprocket of the rear sprocket assembly 612. On the other hand,in the illustrated embodiment, the other sprockets other than thesprocket S and the adjacent sprocket can have any conventionalconfiguration as needed and/or desired. For example, these sprocketsother than the sprocket S and the adjacent sprocket can be each formedas a one-piece, unitary member from a metallic material that is suitablefor a bicycle sprocket such as an iron or an iron alloy. Furthermore,the configuration of the sprocket S and the adjacent sprocket arebasically identical to each other except for the dimensions and thenumber of sprocket teeth. Therefore, in the illustrated embodiment, thefollowing disclosure will basically focus on the configuration of thesprocket S for the sake of brevity, and detailed description of theadjacent sprocket will be omitted for the sake of brevity.

As shown in FIGS. 24 and 25, the sprocket S (e.g., a bicycle sprocket)basically includes a sprocket body 632, and a plurality of sprocketteeth 634. The sprocket body 632 has a rotational axis X1. The sprocketbody 632 includes an outer periphery 636 and an inner periphery 638. Thesprocket teeth 634 extend radially outwardly from the outer periphery636 of the sprocket body 632. In the illustrated embodiment, thesprocket S is the largest sprocket of the rear sprocket assembly 612. Asshown in FIGS. 24 and 25, the total number of the sprocket teeth 634 isthirty-six. Of course, the total number of the sprocket teeth can bedifferent number as needed and/or desired.

In the illustrated embodiment, the sprocket S has a multi-layeredstructure. Specifically, as shown in FIGS. 24 to 26, the sprocket Sincludes a first layered member 642, a second layered member 644, athird layered member 646, and a coating layer 648. In the illustratedembodiment, the first, second and third layered members 642, 644 and 646radially outwardly extends from the inner periphery 638 of the sprocketbody 632 to the sprocket teeth 634. The multi-layered structure of thesprocket S is basically identical to that of the sprocket S inaccordance with the first embodiment, except that the sprocket body 632has a plurality of (e.g., six) axially projecting portions 666 and aplurality of (e.g., six) axially recessed portions 668. Of course, itwill be apparent to those skilled in the art from this disclosure thatthe number of the axially projecting portions 666 can be more than orless than six as needed and/or desired, and that the number of theaxially recessed portions 668 can be more than or less than six asneeded and/or desired. The axially projecting portions 666 and theaxially recessed portions 668 are positioned at the sprocket body 632.In other words, the multi-layered structure of the sprocket teeth 634 ofthe sprocket S is identical to that of the sprocket S in accordance withthe first embodiment. Specifically, the configurations of the first,second and third layered members 642, 644 and 646 and the coating layer648 at the sprocket teeth 634 of the sprocket S are identical to thoseof the first, second and third layered members 42, 44 and 46 and thecoating layer 48 at the sprocket teeth 34 of the sprocket S inaccordance with the first embodiment. Furthermore, the materials of thefirst, second and third layered members 642, 644 and 646 and the coatinglayer 648 of the sprocket S are same as those of the first, second andthird layered members 42, 44 and 46 and the coating layer 48 of thesprocket S in accordance with the first embodiment, respectively. Forexample, the first layered member 642 has a specific gravity that isless than those of the second layered member 644 and the third layeredmember 646. Thus, the detailed description of the multi-layeredstructure of the sprocket S will be omitted for the sake of brevity. Itwill be apparent to those skilled in the art from this disclosure thatthe descriptions and illustrations of the parts of sprocket S inaccordance with the first embodiment also apply to the parts of thesprocket S having the same name, except as discussed and/or illustratedherein.

In the illustrated embodiment, the first layered member 642 has a firstaxial surface and a second axial surface opposite to the first axialsurface. The second layered member 644 is attached to the first axialsurface of the first layered member 642. The third layered member 646 isattached to the second axial surface of the first layered member 642.The coating layer 648 is formed on a radially end surface of the firstlayered member 642. The first, second and third layered members 642, 644and 646 and the coating layer 648 are attached with respect to eachother in the same fixing manner as discussed in the first embodiment.Thus, the detailed description will be omitted for the sake of brevity.

As shown in FIG. 26, the first and third layered members 642 and 646 aregenerally a flat plate with planer opposite surfaces being planarbetween the inner periphery 638 of the sprocket body 632 to the sprocketteeth 634 other than various holes and recesses. On the other hand, thesecond layered member 644 has the axially projecting portions 666 andthe axially recessed portions 668. The axially projecting portions 666and the axially recessed portions 668 are formed at locationscircumferentially spaced from each other at predetermined interval aboutthe inner periphery 638 of the sprocket body 632. Each of the axiallyprojecting portions 666 has a plurality of projections 666 a that isformed on one axial side of the second layered member 644. Theprojections 666 a of the axially projecting portions 666 define theaxially recessed portions 668 on the other axial side of the secondlayered member 644. In particular, in the illustrated embodiment, asshown in FIG. 26, each of the axially projecting portions 666 bulgesaway from the first and third layered members 642 and 646, which definesthe axially recessed portions 668 that are recessed away from the firstand third layered members 642 and 646. In the illustrated embodiment,the second layered member 644 is integrally formed as a one-piece,unitary member.

As shown in FIG. 24 to 26, the first and second layered members 642 and644 overlap each other in an axial direction as viewed parallel to therotational axis X1. Furthermore, in the illustrated embodiment, thefirst and second layered members 642 and 644 do not overlap each otherin a radial direction as viewed perpendicularly to the rotational axisX1. On the other hand, the first and third layered members 642 and 646overlap each other in the axial direction as viewed parallel to therotational axis X1. Furthermore, the first and third layered members 642and 646 do not overlap each other in the radial direction as viewedperpendicularly to the rotational axis X1 at least at the sprocket teeth634 of the sprocket S. As shown in FIG. 26, the first layered member 642includes a plurality of (e.g., six) notches 682 that iscircumferentially spaced from each other at predetermined interval aboutthe inner periphery 638 of the sprocket body 632. Furthermore, the thirdlayered member 646 includes a plurality of (e.g., six) notches 684 thatis circumferentially spaced from each other at predetermined intervalabout the inner periphery 638 of the sprocket body 632. Of course, itwill be apparent to those skilled in the art from this disclosure thatthe numbers of the notches 682 and 684 can be more than or less than sixas needed and/or desired. The notches 682 of the first layered member642 are formed at locations corresponding to the notches 684 of thethird layered member 646. Specifically, in the illustrated embodiment,the first and third layered members 642 and 646 have an identical shape.Thus, inner surfaces of the axially recessed portions 668 of the secondlayered member 644 are axially exposed through the notches 682 of thefirst layered member 642 and through the notches 684 of the thirdlayered member 646, respectively, in the axial direction as viewedparallel to the rotational axis X1. In other words, in the illustratedembodiment, the sprocket body 632 includes the first layered member 642,the second layered member 644 and the third layered member 646 at thearea except for the axially recessed portions 668. Thus, as shown inFIGS. 24 to 26, the sprocket body 632 only includes the second layeredmember 644 at the axially recessed portions 668.

As mentioned above, the rear sprocket assembly 612 includes the sprocketS and the adjacent sprocket (e.g., a plurality of bicycle sprockets).The sprocket S and the adjacent sprocket are detachably coupled to eachother. Specifically, similar to the rear sprocket assembly 312 shown inFIG. 18B, the axially projecting portions 666 of the sprocket S (e.g.,one of the bicycle sprockets) mates with axially recessed portions ofthe adjacent sprocket (e.g., an adjacent one of the bicycle sprockets)adjacent to the sprocket S (e.g., one of the bicycle sprockets) whilethe sprocket S and the adjacent sprocket (e.g., bicycle sprockets) areattached to each other. Specifically, in the illustrated embodiment, anouter profile of each of the axially projecting portions 666 of thesprocket S is dimensioned to match with an inner profile of respectiveone of the axially recessed portion of the adjacent sprocket. Thus, thesprocket S and the adjacent sprocket are fittedly and detachably coupledto each other. Furthermore, an axial height of the axially projectingportions 666 of the sprocket S and an axial depth of the axiallyrecessed portions of the adjacent sprocket are dimensioned such that thesprocket S and the adjacent sprocket are axially spaced from each otherat a predetermined interval.

In the illustrated embodiment, the sprocket S includes the first layeredmember 642, the second layered member 644, the third layered member 646,and the coating layer 648. However, the multi-layered structure of thesprocket S is not limited to this. The sprocket S can only include thefirst layered member 642, the second layered member 644 and the thirdlayered member 646 without the coating layer 648. Furthermore, thesprocket S can only include the first layered member 642, the secondlayered member 644 and the coating layer 648 without the third layeredmember 646. In this case, a third axial surface of the second layeredmember 644 is attached to the first axial surface of the first layeredmember 642. However, the second axial surface of the first layeredmember 642 and a fourth axial surface of the second layered member 644that is opposite the third axial surface are exposed.

In the illustrated embodiment, the second layered member 644 has theaxially projecting portions 666 and the axially recessed portions 668.However, alternatively, the third layered member 646 can have theaxially projecting portions and the axially recessed portions. In thiscase, the axially projecting portions of the third layered member extendthrough the notches of the first and second layered members 642 and 644,respectively, and protrude beyond the second layered member 644.

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. The term “attached” or “attaching”, as used herein,encompasses configurations in which an element directly secured toanother element by affixing the element is directly to the otherelement; configurations in which the element is indirectly secured tothe other element by affixing the element to the intermediate member(s)which in turn are affixed to the other element; and configurations inwhich one element is integral with another element, i.e. one element isessentially part of the other element. This definition also applies towords of similar meaning, for example, “joined”, “connected”, “coupled”,“mounted”, “bonded”, “fixed” and their derivatives. The term “layeredmember”, as used herein, means structure comprising a plurality ofsubstantial layers that are overlapped with each other, but suchsubstantial layers do not encompass very thin coating such as platedmembranes. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Also, it will be understood thatalthough the terms “first” and “second” may be used herein to describevarious components these components should not be limited by theseterms. These terms are only used to distinguish one component fromanother. Thus, for example, a first component discussed above could betermed a second component and vice-a-versa without departing from theteachings of the present invention. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean anamount of deviation of the modified term such that the end result is notsignificantly changed.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. For example, this invention can be applied for notonly a rotary type of a bicycle electric operating device such asdescribed in the illustrated embodiments but can also be applied to anykind of bicycle electric operating device. Moreover, the size, shape,location or orientation of the various components can be changed asneeded and/or desired so long as they do not substantially theirintended function. Components that are shown directly connected orcontacting each other can have intermediate structures disposed betweenthem unless specifically stated otherwise. The functions of one elementcan be performed by two, and vice versa unless specifically statedotherwise. The structures and functions of one embodiment can be adoptedin another embodiment. It is not necessary for all advantages to bepresent in a particular embodiment at the same time. Every feature whichis unique from the prior art, alone or in combination with otherfeatures, also should be considered a separate description of furtherinventions by the applicant, including the structural and/or functionalconcepts embodied by such feature(s). Thus, the foregoing descriptionsof the embodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A bicycle sprocket comprising: a sprocket bodyhaving a rotational axis; and a plurality of sprocket teeth extendingradially outwardly from an outer periphery of the sprocket body, atleast one of the sprocket teeth including a first layered member, asecond layered member and a third layered member, the first, second andthird layered members each being constructed of a metallic material, thefirst layered member having a first axial surface and a second axialsurface opposite to the first axial surface, the second layered memberbeing attached to the first axial surface of the first layered membersuch that the first and second layered members overlap each other in anaxial direction as viewed parallel to the rotational axis, the thirdlayered member being attached to the second axial surface of the firstlayered member such that the first and third layered members overlapeach other in the axial direction as viewed parallel to the rotationalaxis, the first layered member having a specific gravity that is lessthan those of the second layered member and the third layered member. 2.The bicycle sprocket according to claim 1, wherein each of the first,second and third layered members has an axial thickness more than orequal to 0.1 mm.
 3. The bicycle sprocket according to claim 1, whereinthe first and second layered members do not overlap each other in aradial direction as viewed perpendicularly to the rotational axis, andthe first and third layered members do not overlap each other in theradial direction as viewed perpendicularly to the rotational axis. 4.The bicycle sprocket according to claim 1, wherein the sprocket bodyincludes the first layered member, the second layered member and thethird layered member.
 5. The bicycle sprocket according to claim 1,wherein the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.
 6. Thebicycle sprocket according to claim 5, wherein the second and thirdlayered members are made of iron.
 7. The bicycle sprocket according toclaim 6, wherein the second and third layered members are made ofstainless steel.
 8. The bicycle sprocket according to claim 5, whereinthe first layered member is made of quenched aluminum.
 9. The bicyclesprocket according to claim 1, wherein the first layered member is madeof non-metallic material.
 10. The bicycle sprocket according to claim 9,wherein the non-metallic material of the first layered member includesresin.
 11. The bicycle sprocket according to claim 10, wherein thenon-metallic material of the first layered member is fiber-reinforcedmaterial.
 12. The bicycle sprocket according to claim 10, wherein thefirst layered member and the second layered member are attached to eachother by an integral molding process, and the first layered member andthe third layered member are attached to each other by an integralmolding process.
 13. The bicycle sprocket according to claim 9, whereinthe second and third layered members are made of iron.
 14. The bicyclesprocket according to claim 13, wherein the second and third layeredmembers are made of stainless steel.
 15. The bicycle sprocket accordingto claim 1, wherein the second and third layered members are made ofiron.
 16. The bicycle sprocket according to claim 15, wherein the secondand third layered members are made of stainless steel.
 17. The bicyclesprocket according to claim 16, wherein the second and third layeredmembers each have Vickers hardness larger than or equal to 400 (HV),respectively.
 18. The bicycle sprocket according to claim 1, wherein thefirst layered member and the second layered member are attached to eachother by diffusion bonding, and the first layered member and the thirdlayered member are attached to each other by diffusion bonding.
 19. Thebicycle sprocket according to claim 1, wherein the first layered memberand the second layered member are attached to each other with anadhesive, and the first layered member and the third layered member areattached to each other with an adhesive.
 20. The bicycle sprocketaccording to claim 1, wherein the plurality of sprocket teeth includesthe first layered member, the second layered member and the thirdlayered member.
 21. The bicycle sprocket according to claim 1, whereinthe second layered member has a specific gravity that is equal to thatof the third layered member.
 22. The bicycle sprocket according to claim1, wherein the at least one of the sprocket teeth further includes acoating layer formed on a radially end surface of the first layeredmember.
 23. The bicycle sprocket according to claim 1, wherein the firstlayered member extends radially inwardly from an inner periphery of thesprocket body, and the first layered member has an axially projectingportion and an axially recessed portion, the axially projecting portionand the axially recessed portion being positioned radially inwardly fromthe inner periphery of the sprocket body.
 24. The bicycle sprocketaccording to claim 23, wherein the first layered member has a bicyclehub engaging profile at a location of a radially inner end of the firstlayered member.
 25. A multiple sprocket assembly comprising: a pluralityof the bicycle sprockets according to claim 23, the axially projectingportion of one of the bicycle sprockets mating with the axially recessedportion of an adjacent one of the bicycle sprockets adjacent to the oneof the bicycle sprockets while the bicycle sprockets are attached toeach other.
 26. The bicycle sprocket according to claim 1, wherein thesprocket body has an axially projecting portion and an axially recessedportion, the axially projecting portion and the axially recessed portionbeing positioned at the sprocket body.
 27. A multiple sprocket assemblycomprising: a plurality of the bicycle sprockets according to claim 26,the axially projecting portion of one of the bicycle sprockets matingwith the axially recessed portion of an adjacent one of the bicyclesprockets adjacent to the one of the bicycle sprockets while the bicyclesprockets are attached to each other.
 28. A multiple sprocket assemblycomprising: a plurality of the bicycle sprockets according to claim 1;and a sprocket support member to which the bicycle sprockets aremounted.
 29. The multiple sprocket assembly according to claim 28,wherein the sprocket support member has a unitary one-piece structure.30. A bicycle sprocket comprising: a sprocket body having a rotationalaxis; and a plurality of sprocket teeth extending radially outwardlyfrom an outer periphery of the sprocket boyd, at least one of thesprocket teeth including a first layered member, a second layered membera third layered member and a coating layer formed on a radially endsurface of the first layered member, the coating layer being anintermetallic compound layer, the first layered member having a firstaxial surface and a second axial surface opposite to the first axialsurface, the second layered member being attached to the first axialsurface of the first layered member such that the first and secondlayered members overlap each other in an axial direction as viewedparallel to the rotational axis, the third layered member being attachedto the second axial surface of the first layered member such that thefirst and third layered members overlap each other in the axialdirection as viewed parallel to the rotational axis, the first layeredmember having a specific gravity that is less than those of the secondlayered member and the third layered member.
 31. The bicycle sprocketaccording to claim 30, wherein the intermetallic compound layer is madeof aluminum, and one of nickel and iron.
 32. A bicycle sprocketcomprising: a sprocket body having a rotational axis; and a plurality ofsprocket teeth extending radially outwardly from an outer periphery ofthe sprocket body, at least one of the sprocket teeth including a firstlayered member, a second layered member, a third layered member and acoating layer formed on a radially end surface of the first layeredmember, the coating layer being a plated layer, the first layered memberhaving a first axial surface and a second axial surface opposite to thefirst axial surface, the second layered member being attached to thefirst axial surface of the first layered member such that the first andsecond layered members overlap each other in an axial direction asviewed parallel to the rotational axis, the third layered member beingattached to the second axial surface of the first layered member suchthat the first and third layered members overlap each other in the axialdirection as viewed parallel to the rotational axis, the first layeredmember having a specific gravity that is less than those of the secondlayered member and the third layered member.
 33. The bicycle sprocketaccording to claim 32, wherein the coating layer is a nickel-platedlayer.
 34. A bicycle sprocket comprising: a sprocket body having arotational axis; and a plurality of sprocket teeth extending radiallyoutwardly from an outer periphery of the sprocket body, at least one ofthe sprocket teeth including a first layered member, a second layeredmember and a coating layer formed on a radially end surface of the firstlayered member, the second layered member having a radially outermostend surface that is free of the coating layer, the first and secondlayered members being attached to each other such that the first andsecond layered members overlap each other in an axial direction asviewed parallel to the rotational axis and such that the first andsecond layered members do not overlap each other in a radial directionas viewed perpendicularly to the rotational axis, the first layeredmember having a specific gravity that is less than that of the secondlayered member.
 35. The bicycle sprocket according to claim 34, whereineach of the first and second layered members has an axial thickness morethan or equal to 0.1 mm.
 36. The bicycle sprocket according to claim 34,wherein the sprocket body includes the first layered member and thesecond layered member.
 37. The bicycle sprocket according to claim 34,wherein the first layered member is made of a material selected from thegroup consisting of aluminum, titanium, magnesium and beryllium.
 38. Thebicycle sprocket according to claim 37, wherein the first layered memberis made of quenched aluminum.
 39. The bicycle sprocket according toclaim 34, wherein the second layered member is made of iron.
 40. Thebicycle sprocket according to claim 39, wherein the second layeredmember is made of stainless steel.
 41. The bicycle sprocket according toclaim 40, wherein the first layered member is made of a materialselected from the group consisting of aluminum, titanium, magnesium andberyllium.
 42. The bicycle sprocket according to claim 40, wherein thesecond layered member has Vickers hardness larger than or equal to 400(HV).
 43. The bicycle sprocket according to claim 34, wherein the firstlayered member is made of non-metallic material.
 44. The bicyclesprocket according to claim 43, wherein the non-metallic material of thefirst layered member includes resin.
 45. The bicycle sprocket accordingto claim 44, wherein the non-metallic material of the first layeredmember is fiber-reinforced material.
 46. The bicycle sprocket accordingto claim 44, wherein the first layered member and the second layeredmember are attached to each other by an integral molding process. 47.The bicycle sprocket according to claim 43, wherein the second layeredmember is made of iron.
 48. The bicycle sprocket according to claim 47,wherein the second layered member is made of stainless steel.
 49. Thebicycle sprocket according to claim 34, wherein the first layered memberand the second layered member are attached to each other by diffusionbonding.
 50. The bicycle sprocket according to claim 34, wherein thefirst layered member and the second layered member are attached to eachother with an adhesive.
 51. The bicycle sprocket according to claim 34,wherein the second layered member is attached to the first axial surfaceof the first layered member, and the at least one of the sprocket teethfurther includes a third layered member, the third layered member beingattached to the second axial surface of the first layered member suchthat the first and third layered members overlap each other in the axialdirection as viewed parallel to the rotational axis and such that thefirst and third layered members do not overlap each other in the radialdirection as viewed perpendicularly to the rotational axis.
 52. Thebicycle sprocket according to claim 51, wherein the sprocket bodyincludes the first layered member, the second layered member and thethird layered member.
 53. The bicycle sprocket according to claim 34,wherein the plurality of sprocket teeth includes the first layeredmember and the second layered member.
 54. The bicycle sprocket accordingto claim 34, wherein the first layered member extends radially inwardlyfrom an inner periphery of the sprocket body, and the first layeredmember has an axially projecting portion and an axially recessedportion, the axially projecting portion and the axially recessed portionbeing positioned radially inwardly from the inner periphery of thesprocket body.
 55. The bicycle sprocket according to claim 54, whereinthe first layered member has a bicycle hub engaging profile at alocation of a radially inner end of the first layered member.
 56. Thebicycle sprocket according to claim 54, wherein the sprocket bodyincludes the first layered member and the second layered member.
 57. Amultiple sprocket assembly comprising: a plurality of the bicyclesprockets according to claim 54, the axially projecting portion of oneof the bicycle sprockets mating with the axially recessed portion of anadjacent one of the bicycle sprockets adjacent to the one of the bicyclesprockets while the bicycle sprockets are attached to each other. 58.The bicycle sprocket according to claim 34, wherein the sprocket bodyhas an axially projecting portion and an axially recessed portion, theaxially projecting portion and the axially recessed portion beingpositioned at the sprocket body.
 59. A multiple sprocket assemblycomprising: a plurality of the bicycle sprockets according to claim 58,the axially projecting portion of one of the bicycle sprockets matingwith the axially recessed portion of an adjacent one of the bicyclesprockets adjacent to the one of the bicycle sprockets while the bicyclesprockets are attached to each other.
 60. A multiple sprocket assemblycomprising: a plurality of the bicycle sprockets according to claim 34;and a sprocket support member to which the bicycle sprockets aremounted.
 61. The multiple sprocket assembly according to claim 60,wherein the sprocket support member has a unitary one-piece structure.62. A bicycle sprocket comprising: a sprocket body having a rotationalaxis; and a plurality of sprocket teeth extending radially outwardlyfrom an outer periphery of the sprocket body, at least one of thesprocket teeth including a first layered member, a second layeredmember, a third layered member and a coating layer formed on a radiallyend surface of the first layered member, the coating layer being anintermetallic compound layer, the first layered member having a firstaxial surface and a second axial surface opposite to the first axialsurface, the second layered member being attached to the first axialsurface of the first layered member such that the first and secondlayered members overlap each other in an axial direction as viewedparallel to the rotational axis, the third layered member being attachedto the second axial surface of the first layered member such that thefirst and third layered members overlap each other in the axialdirection as viewed parallel to the rotational axis, the first layeredmember having a specific gravity that is less than those of the secondlayered member and the third layered member.
 63. The bicycle sprocketaccording to claim 62, wherein the intermetallic compound layer is madeof aluminum, and one of nickel and iron.
 64. A bicycle sprocketcomprising: a sprocket body having a rotational axis; and a plurality ofsprocket teeth extending radially outward from an outer periphery of thesprocket body, at least one of the sprocket teeth including a firstlayered member, a second layered member, a third layered member and acoating layer formed on a radially end surface of the first layermember, the coating layer being a plated layer, the first layered memberhaving a first axial surface and a second axial surface opposite to thefirst axial surface, the second layered member being attached to thefirst axial surface of the first layered member such that the first andsecond layered members overlap each other in an axial direction asviewed parallel to the rotational axis, the third layered member beingattached to the second axial surface of the first layered member suchthat the first and third layered members overlap each other in the axialdirection as viewed parallel to the rotational axis, the first layeredmember having a specific gravity that is less than those of the secondlayered member and the third layered member.
 65. The bicycle sprocketaccording to claim 64, wherein the coating layer is a nickel-platedlayer.